[clang][driver] Support -x for all languages in CL mode

After llvm#68921,
clang-cl gained option `-x` but only for CUDA/HIP.
This commit simply removes the restriction on parameters to `-x`.
Especially, it is able to use `-x c++-module` and `-x c++-system-header`
to build C++20 modules and header units with clang-cl.

This effectively reverts commit fe08212.

Closes llvm#88006.

clang/lib/Driver/Driver.cpp

@@ -2636,22 +2636,13 @@ void Driver::BuildInputs(const ToolChain &TC, DerivedArgList &Args,
  Diag(clang::diag::note_drv_t_option_is_global);
  }
 
- // CUDA/HIP and their preprocessor expansions can be accepted by CL mode.
  // Warn -x after last input file has no effect
- auto LastXArg = Args.getLastArgValue(options::OPT_x);
- const llvm::StringSet<> ValidXArgs = {"cuda", "hip", "cui", "hipi"};
- if (!IsCLMode() || ValidXArgs.contains(LastXArg)) {
+ {
  Arg *LastXArg = Args.getLastArgNoClaim(options::OPT_x);
  Arg *LastInputArg = Args.getLastArgNoClaim(options::OPT_INPUT);
  if (LastXArg && LastInputArg &&
  LastInputArg->getIndex() < LastXArg->getIndex())
  Diag(clang::diag::warn_drv_unused_x) << LastXArg->getValue();
- } else {
- // In CL mode suggest /TC or /TP since -x doesn't make sense if passed via
- // /clang:.
- if (auto *A = Args.getLastArg(options::OPT_x))
- Diag(diag::err_drv_unsupported_opt_with_suggestion)
- << A->getAsString(Args) << "/TC' or '/TP";
  }
 
  for (Arg *A : Args) {

clang/test/Driver/x-args.c

@@ -6,6 +6,4 @@
 // RUN: %clang -fsyntax-only %s -xc %s -xc++ -fsyntax-only 2>&1 | FileCheck %s
 // CHECK: '-x c++' after last input file has no effect
 
-// RUN: not %clang_cl /WX /clang:-xc /clang:-E /clang:-dM -- %s 2>&1 | FileCheck --implicit-check-not="error:" -check-prefix=CL %s
-// RUN: not %clang_cl /TC /WX /clang:-xc /clang:-E /clang:-dM -- %s 2>&1 | FileCheck --implicit-check-not="error:" -check-prefix=CL %s
-// CL: error: unsupported option '-x c'; did you mean '/TC' or '/TP'?
+// RUN: %clang_cl -fsyntax-only /WX -xc++ -- %s