Need to improve gr-audio/lib/CMakeLists.txt so that it no longer automagically enables support for ALSA, JACK, OSS and PortAudio based on the presence of media-libs/alsa-lib, media-sound/jack-audio-connection-kit, sys-kernel/linux-headers and media-libs/portaudio.
Created attachment 315141 [details, diff] gnuradio-3.6.1-automagic-audio.patch first attempt
Fixed in 3.6.1-r1