[clang][driver][MSVC] clang-cl's handling of /external:W0 is different from that of MSVC #155297
Description
Description
/external:W0 is used to disable warnings from external/system headers in MSVC (https://learn.microsoft.com/en-us/cpp/build/reference/external-external-headers-diagnostics?view=msvc-170). It does not have any effect on #pragma messages(). However, unlike MSVC, clang-cl disables pragma messages upon receiving /external:W0.
Example
Here's a working example: https://godbolt.org/z/Mb4c5zfax