Leftover code in `sysconfig.expand_makefile_vars`

[picnixz]

Bug report

Bug description:

I think there is some leftover code in sysconfig.expand_makefile_vars (90d02e5):

cpython/Lib/sysconfig/__init__.py

Lines 727 to 734 in 4dade05

	while True:
	m = re.search(_findvar1_rx, s) or re.search(_findvar2_rx, s)
	if m:
	(beg, end) = m.span()
	s = s[0:beg] + vars.get(m.group(1)) + s[end:]
	else:
	break
	return s

The _findvar1_rx and _findvar2_rx variables are not declared at all (they were moved to sysconfig/__main__.py). Since the function is publicly named (but not exported nor documented), I prefer backporting the changes of #110785, namely re-use the patterns as is.

cc @FFY00

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-128978: Fix a NameError in sysconfig.expand_makefile_vars #128979