gh-99942: python.pc on android/cygwin should link to libpython per configure.ac (GH-100356)

In commit 254b309c801f82509597e3d7d4be56885ef94c11 a previous change to avoid linking to libpython was partially reverted for Android (and later Cygwin as well), to add back the link flags. This was applied to distutils and to python-config.sh, but not to python.pc.

Add it back to python.pc as well.

Automerge-Triggered-By: GH:gpshead