• Fix the build when audio/oss is installed by force to search for sys/soundcard.h in /usr/include first rather than oss's header. [1]
• While I am here, fix the flac option. The autocheck is not need when it is enable by default and add --disable-flac to make WITHOUT_FLAC works.

PR: ports/116268 [1]
Reported by: Volker <heizraum@freenet.de> [1]