Free threaded `Python.h` is incompatible with `-masm=intel`

[colesbury]

Bug report

The _Py_ThreadId function uses a mix of inline assembly and intrinsics depending on the platform. We currently use AT&T assembly syntax, which is the default on GCC and Clang. If an extension module builds with -masm=intel, then #include <Python.h> will fail with syntax errors.

GCC and Clang support multiple assembler dialects in inline assembly, so we can provide implementations for both AT&T and Intel syntax.

I think this is probably only relevant for x86/x86-64.

Linked PRs

• gh-145010: Fix Python.h compilation with -masm=intel #145011
• [3.14] gh-145010: Fix Python.h compilation with -masm=intel (GH-145011) #145776