[clang] Add option -fstdlib-hardening= (PR #78763)

[Louis Dionne via cfe-commits]

================
@@ -281,6 +281,7 @@ LANGOPT(OffloadingNewDriver, 1, 0, "use the new driver for generating offloading
 LANGOPT(SYCLIsDevice      , 1, 0, "Generate code for SYCL device")
 LANGOPT(SYCLIsHost        , 1, 0, "SYCL host compilation")
 ENUM_LANGOPT(SYCLVersion  , SYCLMajorVersion, 2, SYCL_None, "Version of the SYCL standard used")
+ENUM_LANGOPT(LibcxxHardeningMode, LibcxxHardeningModeKind, 3, LIBCPP_HARDENING_MODE_NOT_SPECIFIED, "libc++ harderning mode")
----------------
ldionne wrote:

This should be `StdlibHardeningMode` to reflect the option name -- in the future we could potentially expand to libstdc++ as well. I think this applies to a couple of other names throughout the review, too.

https://github.com/llvm/llvm-project/pull/78763