Expose extension compiler requirements in build-details.json

[pablogsal]

CPython's build-details.json should expose the extension compiler flags required or recommended by the interpreter build, including PEP 831's frame-pointer choice. This gives generic build backends and tools such as cibuildwheel a supported alternative to copying the complete sysconfig CFLAGS value.

Context: python/peps#5074 (comment)

Linked PRs

• gh-155170: Expose extension compiler flags in build details #155172