[libc++] Pass -fno-modules to clang-tidy instead of disabling it for the modules build

[Mordante]

No real objection, but I think having an XFAIL will give us feedback when modules start working with modules.

libcxx/test/libcxx/clang_tidy.sh.cpp

11–12

Let's add a TODO so we can grep to remove it at some point. I expect clang-tidy to work at some point with modules and it might even get module specific diagnostics.

[philnik]

In D128053#3592505, @Mordante wrote:

No real objection, but I think having an XFAIL will give us feedback when modules start working with modules.

I'm using modules for my local build and it's quite annoying having to re-run CMake to be able to run clang-tidy. Since clang doesn't even have complete modules support yet I don't think clang-tidy will work properly with them in the near future.

libcxx/test/libcxx/clang_tidy.sh.cpp

11–12

I'll add one when committing if there are no other objections.

[ldionne]

LGTM with a TODO

libcxx/test/libcxx/clang_tidy.sh.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // REQUIRES: has-clang-tidy
-// XFAIL: modules-build
 
-// RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* -- -Wweak-vtables -Wno-unknown-warning-option %{compile_flags}
+// TODO: run clang-tidy with modules enabled once they are supported
+// RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* -- -Wweak-vtables -Wno-unknown-warning-option %{compile_flags} -fno-modules
 // -Wno-unknown-warning-option tells clang-tidy to ignore '-W' command-line arguments that it doesn't know.
 // There are some GCC-specific ones where clang-tidy would warn otherwise.
 
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
 #    undef __DEPRECATED
 #endif