[libc++][test] Disables clang-tidy test for GCC.

[Mordante]

Summary

Increasing the constexpr evaluation limit breaks this clang-tidy test
for GCC. As discussed in D131317 disable the test in GCC.

[philnik]

LGTM with CI passing.

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
 
+// The GCC compiler flags are not always compatible with clang-tidy.
+// UNSUPPORTED: gcc
+
 // TODO: run clang-tidy with modules enabled once they are supported
-// RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* --config-file=%S/../../.clang-tidy -- -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.
+// RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* --config-file=%S/../../.clang-tidy -- -Wweak-vtables %{compile_flags} -fno-modules
 
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
 #    undef __DEPRECATED
 #endif
 
 /*
 BEGIN-SCRIPT