Patch CC and CCX entries in sysconfig for cross-compiled aarch64 Python distributions

[zanieb]

Closes #12207

[zanieb]

It turns out this is relevant for CC too

❯ docker run -it --rm ghcr.io/astral-sh/uv:0.6.5-bookworm-slim /bin/bash -c "uv run -p 3.13 -m sysconfig | grep CC"
	CC = "/usr/bin/aarch64-linux-gnu-gcc"

We just were never patching these (and it didn't matter because people are happy with GCC)

I broke this upstream in astral-sh/python-build-standalone#545 because I defined CXX as the host compiler instead of the target per this comment astral-sh/python-build-standalone#545 (comment) — we can change that upstream.

I'm unsure if it'd be disruptive to ship this change. It seems more correct.

[zanieb]

This is also going to be a problem for other cross-compiles like, s390x, e.g., the values will be

  host_cc: /usr/bin/x86_64-linux-gnu-gcc
  host_cxx: /usr/bin/x86_64-linux-gnu-g++
  target_cc: /usr/bin/s390x-linux-gnu-gcc

[zanieb]

Here's the upstream fix astral-sh/python-build-standalone#563

Though we may still want to pursue this — we'll need to handle more patterns for it to be robust.

[samypr100]

If we could define the authoritative list of variants being targets.yml, I wonder if we could use it to autogen the replacements on uv side automatically