gh-159759: Fix libpython.static in PEP 739 build-details.json (#159766)

When a shared library is also built, point `libpython.static` at `LIBPL`,
the only place `make install` puts the static library, and don't list it for
framework builds, which don't install one. Static-only builds keep the
existing `LIBDIR` value, which is installed in that configuration.