pyconfig.h string values are double-quoted in sysconfigdat

[stefanor]

Bug report

Bug description:

Noticed in https://github.com/python/cpython/pull/122917/changes#r2478290584

$ python3 -m sysconfig | grep '= ""[^$]'
	PY_BUILTIN_HASHLIB_HASHES = ""md5,sha1,sha2,sha3,blake2""

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-150208: Avoid double-quoting string values in sysconfigdata #150209
• [3.15] gh-150208: Avoid double-quoting string values in sysconfigdata (GH-150209) #154773

[encukou]

I'll backport to 3.15; tests in #154772 need this.

I don't think we should backport to 3.14 at this point. This is a bugfix, but also a functionality change.