SCons: Generate android_source.zip during build

This is now needed after #27781, as this android_source.zip template
is used for custom Android builds from the editor.

platform/android/SCsub

@@ -55,3 +55,25 @@ if lib_arch_dir != '':
 
     stl_lib_path = str(env['ANDROID_NDK_ROOT']) + '/sources/cxx-stl/llvm-libc++/libs/' + lib_arch_dir + '/libc++_shared.so'
     env_android.Command(out_dir + '/libc++_shared.so', stl_lib_path, Copy("$TARGET", "$SOURCE"))
+
+# Zip android/java folder for the source export template.
+print("Archiving platform/android/java as bin/android_source.zip...")
+import os
+import zipfile
+# Change dir to avoid have zipped paths start from the android/java folder.
+olddir = os.getcwd()
+os.chdir(Dir('#platform/android/java').abspath)
+bindir = Dir('#bin').abspath
+# Make 'bin' dir if missing, can happen on fresh clone.
+if not os.path.exists(bindir):
+    os.makedirs(bindir)
+zipf = zipfile.ZipFile(os.path.join(bindir, 'android_source.zip'), 'w', zipfile.ZIP_DEFLATED)
+exclude_dirs = ['.gradle', 'build', 'libs', 'patches']
+for root, dirs, files in os.walk('.', topdown=True):
+    # Change 'dirs' in place to exclude folders we don't want.
+    # https://stackoverflow.com/a/19859907
+    dirs[:] = [d for d in dirs if d not in exclude_dirs]
+    for f in files:
+        zipf.write(os.path.join(root, f))
+zipf.close()
+os.chdir(olddir)