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

[Florian Mayer via llvm-commits]

fmayer wrote:

Hmm I can merge it manually. The GitHub UI still shows "This commit will be authored by giordano at users.noreply.github.com"

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