This test asserted that libz.so.1 was in /lib/*-linux-gnu* or
/usr/lib/*-linux-gnu*, but on non-Debian operating systems it could
equally well be in /usr/lib32, /usr/lib, /usr/lib64 or even /usr/libx32.
Should fix a test failure reported by @denittis on Arch Linux. @denittis, please check?