[compiler-rt] [compiler-rt] Define `__STDC_FORMAT_MACROS` to ensure `PRId64` is available (PR #102980)

[Mosè Giordano via llvm-commits]

giordano wrote:

I should have addressed all issues mentioned above.

To further motivate this PR, note that `__STDC_FORMAT_MACROS` is already defined in other files of compiler-rt for the same reason: https://github.com/llvm/llvm-project/blob/b368404dee8c341dc022a9e9a868f5a268e92033/compiler-rt/lib/gwp_asan/optional/segv_handler_posix.cpp#L15-L19

https://github.com/llvm/llvm-project/pull/102980