[cmake] Fix detecting -Wno-pass-failed

If testing for a warning option like -Wno-<foo> with GCC, GCC won't
print any diagnostic at all, leading to the options being accepted
incorrectly. However later, if compiling a file that actually prints
another warning, GCC will also print warnings about these -Wno-<foo>
options being unrecognized.

This avoids extra warning spam like this, for every source file that
does produce warnings with GCC:

    At global scope:
    cc1plus: note: unrecognized command-line option ‘-Wno-pass-failed’ may have been intended to silence earlier diagnostics

This used to be how most warning options were detected in
HandleLLVMOptions.cmake. However, in
4feae05, many of these checks
were rewritten to avoid trying compilation and just relying on
hardcoded knowledge about which compilers and versions thereof
support which warnings, to speed up the cmake configuration.

See e546bbf for an earlier
fix of similar options (for LLDB).

Author: mstorsjo

llvm/cmake/modules/HandleLLVMOptions.cmake

@@ -968,7 +968,8 @@ if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
   # projects and may be injected by pragmas in libstdc++.
   # FIXME: Reconsider this choice if warnings from STL headers can be reliably
   # avoided (https://github.com/llvm/llvm-project/issues/157666).
-  add_flag_if_supported("-Wno-pass-failed" NO_PASS_FAILED_FLAG)
+  check_cxx_compiler_flag("-Wpass-failed" PASS_FAILED_FLAG)
+  append_if(PASS_FAILED_FLAG "-Wno-pass-failed" CMAKE_CXX_FLAGS)
 endif (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
 
 if (LLVM_COMPILER_IS_GCC_COMPATIBLE AND NOT LLVM_ENABLE_WARNINGS)