Fixes stderr silence; adds missing quote from exe args(windows)

https://github.com/godotengine/godot/blob/8d117b214f2bcd14015532fdfbed9b3f059da0e6/core/bind/core_bind.cpp#L452
This function calls the bottom function

https://github.com/godotengine/godot/blob/8d117b214f2bcd14015532fdfbed9b3f059da0e6/drivers/unix/os_unix.cpp#L312

OS.execute doesn't send out a value to stderr, so stderr defaults to
false, which will invoke this bottom line and always silence stderr.

https://github.com/godotengine/godot/blob/8d117b214f2bcd14015532fdfbed9b3f059da0e6/drivers/unix/os_unix.cpp#L315

Some programs, such as FFmpeg, will print out to stderr with valuable
and vital information. This fixes stderr always being silenced, user can
now opt to have it be read as normal.

core/bind/core_bind.cpp

@@ -442,14 +442,14 @@ Error _OS::shell_open(String p_uri) {
 	return OS::get_singleton()->shell_open(p_uri);
 };
 
-int _OS::execute(const String &p_path, const Vector<String> &p_arguments, bool p_blocking, Array p_output) {
+int _OS::execute(const String &p_path, const Vector<String> &p_arguments, bool p_blocking, Array p_output, bool p_read_stderr) {
 
 	OS::ProcessID pid = -2;
 	List<String> args;
 	for (int i = 0; i < p_arguments.size(); i++)
 		args.push_back(p_arguments[i]);
 	String pipe;
-	Error err = OS::get_singleton()->execute(p_path, args, p_blocking, &pid, &pipe);
+	Error err = OS::get_singleton()->execute(p_path, args, p_blocking, &pid, &pipe, NULL, p_read_stderr);
 	p_output.clear();
 	p_output.push_back(pipe);
 	if (err != OK)
@@ -1173,7 +1173,7 @@ void _OS::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_processor_count"), &_OS::get_processor_count);
 
 	ClassDB::bind_method(D_METHOD("get_executable_path"), &_OS::get_executable_path);
-	ClassDB::bind_method(D_METHOD("execute", "path", "arguments", "blocking", "output"), &_OS::execute, DEFVAL(Array()));
+	ClassDB::bind_method(D_METHOD("execute", "path", "arguments", "blocking", "output", "read_stderr"), &_OS::execute, DEFVAL(Array()), DEFVAL(false));
 	ClassDB::bind_method(D_METHOD("kill", "pid"), &_OS::kill);
 	ClassDB::bind_method(D_METHOD("shell_open", "uri"), &_OS::shell_open);
 	ClassDB::bind_method(D_METHOD("get_process_id"), &_OS::get_process_id);

core/bind/core_bind.h

@@ -214,7 +214,7 @@ public:
 	bool is_in_low_processor_usage_mode() const;
 
 	String get_executable_path() const;
-	int execute(const String &p_path, const Vector<String> &p_arguments, bool p_blocking, Array p_output = Array());
+	int execute(const String &p_path, const Vector<String> &p_arguments, bool p_blocking, Array p_output = Array(), bool p_read_stderr = false);
 
 	Error kill(int p_pid);
 	Error shell_open(String p_uri);

platform/windows/os_windows.cpp

@@ -2451,7 +2451,13 @@ Error OS_Windows::execute(const String &p_path, const List<String> &p_arguments,
 
 		for (const List<String>::Element *E = p_arguments.front(); E; E = E->next()) {
 
-			argss += String(" \"") + E->get() + "\"";
+			argss += " \"" + E->get() + "\"";
+		}
+
+		argss += "\"";
+
+		if (read_stderr) {
+			argss += " 2>&1"; // Read stderr too
 		}
 
 		FILE *f = _wpopen(argss.c_str(), L"r");