detect .C as c; fixes #2109

emcc

@@ -56,7 +56,9 @@ from tools.response_file import read_response_file
 # endings = dot + a suffix, safe to test by  filename.endswith(endings)
 C_ENDINGS = ('.c', '.C')
 CXX_ENDINGS = ('.cpp', '.cxx', '.cc', '.CPP', '.CXX', '.CC')
-SOURCE_ENDINGS = C_ENDINGS + CXX_ENDINGS + ('.m', '.mm')
+OBJC_ENDINGS = ('.m',)
+OBJCXX_ENDINGS = ('.mm',)
+SOURCE_ENDINGS = C_ENDINGS + CXX_ENDINGS + OBJC_ENDINGS + OBJCXX_ENDINGS
 BITCODE_ENDINGS = ('.bc', '.o', '.obj')
 DYNAMICLIB_ENDINGS = ('.dylib', '.so', '.dll')
 STATICLIB_ENDINGS = ('.a',)
@@ -714,7 +716,7 @@ use_cxx = True
 for i in range(1, len(sys.argv)):
   arg = sys.argv[i]
   if not arg.startswith('-'):
-    if arg.endswith(('.c','.m')):
+    if arg.endswith(C_ENDINGS + OBJC_ENDINGS):
       use_cxx = False
 
 if '-M' in sys.argv or '-MM' in sys.argv: