Add cc1 option '-fmodule-feature' to add custom values for 'requires' decls

This allows clang-based tools to specify custom features that can be
tested by the 'requires' declaration in a module map file.

llvm-svn: 227868

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1568,6 +1568,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.CurrentModule = Args.getLastArgValue(OPT_fmodule_name);
   Opts.ImplementationOfModule =
       Args.getLastArgValue(OPT_fmodule_implementation_of);
+  Opts.ModuleFeatures = Args.getAllArgValues(OPT_fmodule_feature);
   Opts.NativeHalfType = Opts.NativeHalfType;
   Opts.HalfArgsAndReturns = Args.hasArg(OPT_fallow_half_arguments_and_returns);
   Opts.GNUAsm = !Args.hasArg(OPT_fno_gnu_inline_asm);