Bug 131420

The manpages installed under /usr/local/man for OSS are gzipped twice which causes man <manpage> to only display garbage.

The problem seems to be that the setup.sh script is gzipping the manpages during build and then the manpages get gzipped again when installing the port.
See example:
vista# find . -name "oss*"
./man1/ossmix.1.gz.gz
./man1/ossplay.1.gz.gz
./man1/osstest.1.gz.gz
./man1/ossxmix.1.gz.gz
./man1/ossinfo.1.gz.gz
./man1/osspartysh.1.gz.gz
./man1/ossrecord.1.gz.gz
./man7/oss_audioloop.7.gz.gz
./man7/oss_audiopci.7.gz.gz
./man7/oss_cmi878x.7.gz.gz
./man7/oss_cmpci.7.gz.gz
./man7/oss_cs4281.7.gz.gz
./man7/oss_cs461x.7.gz.gz
./man7/oss_digi96.7.gz.gz
./man7/oss_emu10k1x.7.gz.gz
./man7/oss_envy24.7.gz.gz
./man7/oss_atiaudio.7.gz.gz
./man7/oss_fmedia.7.gz.gz
./man7/oss_geode.7.gz.gz
./man7/oss_hdaudio.7.gz.gz
./man7/oss_ich.7.gz.gz
./man7/oss_imux.7.gz.gz
./man7/oss_midiloop.7.gz.gz
./man7/oss_midimix.7.gz.gz
./man7/oss_sblive.7.gz.gz
./man7/oss_sbpci.7.gz.gz
./man7/oss_sbxfi.7.gz.gz
./man7/oss_trident.7.gz.gz
./man7/oss_via823x.7.gz.gz
./man7/oss_via97.7.gz.gz
./man7/oss_ymf7xx.7.gz.gz
./man7/osscore.7.gz.gz
./man7/oss_ali5455.7.gz.gz
./man7/oss_solo.7.gz.gz
./man7/oss_audigyls.7.gz.gz
./man7/oss_envy24ht.7.gz.gz
./man8/ossdetect.8.gz.gz
./man8/ossdevlinks.8.gz.gz