(Only the first 10 of 27 ports in this commit are shown above. )
Assume "pkg-config zlib" works after 9.x reached EOL
Many ports passed ZLIB_CFLAGS="-I/usr/include" ZLIB_LIBS="-L/usr/lib -lz"
which is unsafe at least with lang/gcc* that override some system headers
and have newer libgcc_s.so that our old version in base may not be