[libc++abi] Mark __cxa_new_handler with _LIBCPP_SAFE_STATIC

For consistency with the other handlers, and because requiring constant
initialization whenever we can is a good thing.

Differential Revision: https://reviews.llvm.org/D110866

GitOrigin-RevId: d9346f525595da11a5a24db3c541efcd95ac3df0
1 file changed