SCons: Fix running 'scons' without platform argument

The cache and progress logic assumed the 'env' to be defined,
but it is only when the selected platform is in the supported list.

Fixes #17497.

(cherry picked from commit a44f9ca545795dc43a59ee284874eac81ac7cbe2)

SConstruct

@@ -432,119 +432,118 @@ else:
     print("\nPlease run scons again with argument: platform=<string>")
 
 
-screen = sys.stdout
-node_count = 0
-node_count_max = 0
-node_count_interval = 1
-if ('env' in locals()):
+# The following only makes sense when the env is defined, and assumes it is
+if 'env' in locals():
+    screen = sys.stdout
+    # Progress reporting is not available in non-TTY environments since it
+    # messes with the output (for example, when writing to a file)
+    show_progress = (env['progress'] and sys.stdout.isatty())
+    node_count = 0
+    node_count_max = 0
+    node_count_interval = 1
     node_count_fname = str(env.Dir('#')) + '/.scons_node_count'
-# Progress reporting is not available in non-TTY environments since it
-# messes with the output (for example, when writing to a file)
-if sys.stdout.isatty():
-    show_progress = env['progress']
-else:
-    show_progress = False
-
-import time, math
-
-class cache_progress:
-    # The default is 1 GB cache and 12 hours half life
-    def __init__(self, path = None, limit = 1073741824, half_life = 43200):
-        self.path = path
-        self.limit = limit
-        self.exponent_scale = math.log(2) / half_life
-        if env['verbose'] == 'yes' and path != None:
-            screen.write('Current cache limit is ' + self.convert_size(limit) + ' (used: ' + self.convert_size(self.get_size(path)) + ')\n')
-        self.delete(self.file_list())
-
-    def __call__(self, node, *args, **kw):
-        global node_count, node_count_max, node_count_interval, node_count_fname, show_progress
-        if show_progress:
-            # Print the progress percentage
-            node_count += node_count_interval
-            if (node_count_max > 0 and node_count <= node_count_max):
-                screen.write('\r[%3d%%] ' % (node_count * 100 / node_count_max))
-                screen.flush()
-            elif (node_count_max > 0 and node_count > node_count_max):
-                screen.write('\r[100%] ')
-                screen.flush()
+
+    import time, math
+
+    class cache_progress:
+        # The default is 1 GB cache and 12 hours half life
+        def __init__(self, path = None, limit = 1073741824, half_life = 43200):
+            self.path = path
+            self.limit = limit
+            self.exponent_scale = math.log(2) / half_life
+            if env['verbose'] == 'yes' and path != None:
+                screen.write('Current cache limit is ' + self.convert_size(limit) + ' (used: ' + self.convert_size(self.get_size(path)) + ')\n')
+            self.delete(self.file_list())
+
+        def __call__(self, node, *args, **kw):
+            global node_count, node_count_max, node_count_interval, node_count_fname, show_progress
+            if show_progress:
+                # Print the progress percentage
+                node_count += node_count_interval
+                if (node_count_max > 0 and node_count <= node_count_max):
+                    screen.write('\r[%3d%%] ' % (node_count * 100 / node_count_max))
+                    screen.flush()
+                elif (node_count_max > 0 and node_count > node_count_max):
+                    screen.write('\r[100%] ')
+                    screen.flush()
+                else:
+                    screen.write('\r[Initial build] ')
+                    screen.flush()
+
+        def delete(self, files):
+            if len(files) == 0:
+                return
+            if env['verbose'] == 'yes':
+                # Utter something
+                screen.write('\rPurging %d %s from cache...\n' % (len(files), len(files) > 1 and 'files' or 'file'))
+            [os.remove(f) for f in files]
+
+        def file_list(self):
+            if self.path == None:
+                # Nothing to do
+                return []
+            # Gather a list of (filename, (size, atime)) within the
+            # cache directory
+            file_stat = [(x, os.stat(x)[6:8]) for x in glob.glob(os.path.join(self.path, '*', '*'))]
+            if file_stat == []:
+                # Nothing to do
+                return []
+            # Weight the cache files by size (assumed to be roughly
+            # proportional to the recompilation time) times an exponential
+            # decay since the ctime, and return a list with the entries
+            # (filename, size, weight).
+            current_time = time.time()
+            file_stat = [(x[0], x[1][0], (current_time - x[1][1])) for x in file_stat]
+            # Sort by the most resently accessed files (most sensible to keep) first
+            file_stat.sort(key=lambda x: x[2])
+            # Search for the first entry where the storage limit is
+            # reached
+            sum, mark = 0, None
+            for i,x in enumerate(file_stat):
+                sum += x[1]
+                if sum > self.limit:
+                    mark = i
+                    break
+            if mark == None:
+                return []
             else:
-                screen.write('\r[Initial build] ')
-                screen.flush()
-
-    def delete(self, files):
-        if len(files) == 0:
-            return
-        if env['verbose'] == 'yes':
-            # Utter something
-            screen.write('\rPurging %d %s from cache...\n' % (len(files), len(files) > 1 and 'files' or 'file'))
-        [os.remove(f) for f in files]
-
-    def file_list(self):
-        if self.path == None:
-            # Nothing to do
-            return []
-        # Gather a list of (filename, (size, atime)) within the
-        # cache directory
-        file_stat = [(x, os.stat(x)[6:8]) for x in glob.glob(os.path.join(self.path, '*', '*'))]
-        if file_stat == []:
-            # Nothing to do
-            return []
-        # Weight the cache files by size (assumed to be roughly
-        # proportional to the recompilation time) times an exponential
-        # decay since the ctime, and return a list with the entries
-        # (filename, size, weight).
-        current_time = time.time()
-        file_stat = [(x[0], x[1][0], (current_time - x[1][1])) for x in file_stat]
-        # Sort by the most resently accessed files (most sensible to keep) first
-        file_stat.sort(key=lambda x: x[2])
-        # Search for the first entry where the storage limit is
-        # reached
-        sum, mark = 0, None
-        for i,x in enumerate(file_stat):
-            sum += x[1]
-            if sum > self.limit:
-                mark = i
-                break
-        if mark == None:
-            return []
-        else:
-            return [x[0] for x in file_stat[mark:]]
-
-    def convert_size(self, size_bytes):
-       if size_bytes == 0:
-           return "0 bytes"
-       size_name = ("bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB")
-       i = int(math.floor(math.log(size_bytes, 1024)))
-       p = math.pow(1024, i)
-       s = round(size_bytes / p, 2)
-       return "%s %s" % (int(s) if i == 0 else s, size_name[i])
-
-    def get_size(self, start_path = '.'):
-        total_size = 0
-        for dirpath, dirnames, filenames in os.walk(start_path):
-            for f in filenames:
-                fp = os.path.join(dirpath, f)
-                total_size += os.path.getsize(fp)
-        return total_size
-
-def progress_finish(target, source, env):
-    global node_count, progressor
-    with open(node_count_fname, 'w') as f:
-        f.write('%d\n' % node_count)
-    progressor.delete(progressor.file_list())
-
-try:
-    with open(node_count_fname) as f:
-        node_count_max = int(f.readline())
-except:
-    pass
-cache_directory = os.environ.get("SCONS_CACHE")
-# Simple cache pruning, attached to SCons' progress callback. Trim the
-# cache directory to a size not larger than cache_limit.
-cache_limit = float(os.getenv("SCONS_CACHE_LIMIT", 1024)) * 1024 * 1024
-progressor = cache_progress(cache_directory, cache_limit)
-Progress(progressor, interval = node_count_interval)
-
-progress_finish_command = Command('progress_finish', [], progress_finish)
-AlwaysBuild(progress_finish_command)
+                return [x[0] for x in file_stat[mark:]]
+
+        def convert_size(self, size_bytes):
+            if size_bytes == 0:
+                return "0 bytes"
+            size_name = ("bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB")
+            i = int(math.floor(math.log(size_bytes, 1024)))
+            p = math.pow(1024, i)
+            s = round(size_bytes / p, 2)
+            return "%s %s" % (int(s) if i == 0 else s, size_name[i])
+
+        def get_size(self, start_path = '.'):
+            total_size = 0
+            for dirpath, dirnames, filenames in os.walk(start_path):
+                for f in filenames:
+                    fp = os.path.join(dirpath, f)
+                    total_size += os.path.getsize(fp)
+            return total_size
+
+    def progress_finish(target, source, env):
+        global node_count, progressor
+        with open(node_count_fname, 'w') as f:
+            f.write('%d\n' % node_count)
+        progressor.delete(progressor.file_list())
+
+    try:
+        with open(node_count_fname) as f:
+            node_count_max = int(f.readline())
+    except:
+        pass
+
+    cache_directory = os.environ.get("SCONS_CACHE")
+    # Simple cache pruning, attached to SCons' progress callback. Trim the
+    # cache directory to a size not larger than cache_limit.
+    cache_limit = float(os.getenv("SCONS_CACHE_LIMIT", 1024)) * 1024 * 1024
+    progressor = cache_progress(cache_directory, cache_limit)
+    Progress(progressor, interval = node_count_interval)
+
+    progress_finish_command = Command('progress_finish', [], progress_finish)
+    AlwaysBuild(progress_finish_command)