Fix .mm file not actually being built.

Author: Ivorforce

SConstruct

@@ -199,6 +199,11 @@ python_sources = set()
 
 sources.update(pathlib.Path('src').glob('**/*.cpp'))
 
+if env['platform'] == 'macos':
+	# For Objective-C++ files
+	env.Append(CCFLAGS = ['-ObjC++'])
+	sources.update(pathlib.Path('src').glob('**/*.mm'))
+
 for ext in ('py', 'pyc', 'json', 'svg', 'md'):
 	python_sources.update(pathlib.Path('lib').glob(f'**/*.{ext}'))
 
@@ -348,9 +353,6 @@ if env['platform'] == 'windows':
 	# linker has trouble if the table is too large
 	env.Append(CPPDEFINES = ['CLASS_VIRTUAL_CALL_TABLE_SIZE=512'])
 elif env['platform'] == 'macos':
-	# For Objective-C++ files
-	env.Append(CCFLAGS = ['-ObjC++'])
-
 	# Need to set the rpath for relative loading of libpython to succeed.
 	# This doesn't work for some reason
 	# env.Replace(RPATH=['@loader_path'])