Fix scons compability on enabling C++ 20 module

SConstruct

@@ -52,6 +52,7 @@ _helper_module("version", "version.py")
 _helper_module("core.core_builders", "core/core_builders.py")
 _helper_module("main.main_builders", "main/main_builders.py")
 _helper_module("misc.utility.color", "misc/utility/color.py")
+_helper_module("misc.utility.compatibility", "misc/utility/compatibility.py")
 
 # Local
 import gles3_builders

drivers/apple_embedded/SCsub

@@ -6,6 +6,7 @@ Import("env")
 env_apple_embedded = env.Clone()
 
 # Enable module support
+# Need a functional export template here, so not using `try_use_cxx20_module`.
 env_apple_embedded.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
 
 # Use bundled Vulkan headers

drivers/metal/SCsub

@@ -1,6 +1,8 @@
 #!/usr/bin/env python
 from misc.utility.scons_hints import *
 
+from misc.utility.compatibility import try_use_cxx20_module
+
 Import("env")
 
 env_metal = env.Clone()
@@ -40,7 +42,10 @@ if "-std=gnu++17" in env_metal["CXXFLAGS"]:
 env_metal.Append(CXXFLAGS=["-std=c++20"])
 
 # Enable module support
-env_metal.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
+if env["platform"] == "macos":
+    try_use_cxx20_module(env_metal)
+else:
+    env_metal.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
 
 # Driver source files
 

misc/utility/compatibility.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python
+
+from methods import is_apple_clang
+
+is_able_to_use_module_cache = None
+
+
+def try_use_cxx20_module(env):
+    """
+    Use C++20's `module` if current compiler supports that.
+    Referencing https://en.cppreference.com/w/cpp/compiler_support/20.
+    """
+    global is_able_to_use_module_cache
+
+    if is_able_to_use_module_cache is not None:
+        return is_able_to_use_module_cache
+    else:
+        is_able_to_use_module_cache = True
+
+        # Apple clang supports module.
+        if is_apple_clang(env):
+            env.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
+        else:
+            is_able_to_use_module_cache = False

platform/ios/SCsub

@@ -3,6 +3,7 @@ from misc.utility.scons_hints import *
 
 from platform_ios_builders import generate_bundle
 
+from misc.utility.compatibility import try_use_cxx20_module
 from platform_methods import combine_libs_apple_embedded
 
 Import("env")
@@ -20,7 +21,8 @@ env_ios = env.Clone()
 ios_lib = env_ios.add_library("ios", ios_lib)
 
 # (iOS) Enable module support
-env_ios.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
+# env_ios.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
+try_use_cxx20_module(env_ios)
 
 combine_command = env_ios.CommandNoCache(
     "#bin/libgodot" + env_ios["LIBSUFFIX"], [ios_lib] + env_ios["LIBS"], env.Run(combine_libs_apple_embedded)

platform/visionos/SCsub

@@ -3,6 +3,7 @@ from misc.utility.scons_hints import *
 
 from platform_visionos_builders import generate_bundle
 
+from misc.utility.compatibility import try_use_cxx20_module
 from platform_methods import combine_libs_apple_embedded
 
 Import("env")
@@ -19,7 +20,8 @@ env_visionos = env.Clone()
 visionos_lib = env_visionos.add_library("visionos", visionos_lib)
 
 # Enable module support
-env_visionos.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
+# env_visionos.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])
+try_use_cxx20_module(env_visionos)
 
 combine_command = env_visionos.Command(
     "#bin/libgodot" + env_visionos["LIBSUFFIX"], [visionos_lib] + env_visionos["LIBS"], combine_libs_apple_embedded