Enable PGO and native builds for aarch64-unknown-linux-gnu

[zanieb]

No description provided.

[indygreg]

We currently don't use a modern LLVM toolchain for Linux aarch64. As a result we won't get the same optimizations from PGO or LTO.

It may just work though since the CPython configure should resolve the appropriate compiler flags from the detected toolchain.

We can look into adopting modern LLVM on Linux ARM separately.

[zanieb]

@indygreg Are you sure? Perhaps I'm misunderstanding but it looks like we cross-compile with LLVM 19

python-build-standalone/pythonbuild/utils.py

Lines 423 to 436 in 0be0a57

	def clang_toolchain(host_platform: str, target_triple: str) -> str:
	if host_platform == "linux64":
	# musl currently has issues with LLVM 15+.
	if "musl" in target_triple:
	return "llvm-14-x86_64-linux"
	else:
	return "llvm-19-x86_64-linux"
	elif host_platform == "macos":
	if platform.mac_ver()[2] == "arm64":
	return "llvm-aarch64-macos"
	else:
	return "llvm-x86_64-macos"
	else:
	raise Exception("unhandled host platform")

https://github.com/astral-sh/python-build-standalone/actions/runs/12677576491/job/35333290679

[zanieb]

Okay after some poking around this is blocked by the Dockerfile which cannot be built on aarch64 yet.