If CFLAGS are set during configure, they are not propagated to the clang invocation to build the JIT stencils. This is problematic for downstream consumers, e.g., inpython-build-standalone where we're using an isolated build system and the clang invocation fails to find required includes.

Linked PRs

• gh-134273: Propagate CFLAGS to the JIT #134274
• gh-134273: Propagate CFLAGS to the JIT #134276