Previously, we patched pkg-config .pc files to have the absolute path to
the directory where we unpack a python-build-standalone release. As
discussed in #11028, we can use ${pcfiledir} in a .pc file to indicate
paths relative to the location of the file itself.
This change was implemented in astral-sh/python-build-standalone#507, so
for newer python-build-standalone releases, we don't need to do any
patching. Optimize this case by only modifying the .pc file if an actual
change is needed (which might be helpful down the line with hard links
or something). For older releases, change uv's patch to match what
python-build-standalone now does.
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