Add cmake options to require specific backends Note that this alone doesn't gurantee run-time availability for backends libs that are loaded at run-time.
Add cmake options to require specific backends
Note that this alone doesn't gurantee run-time availability for backends libs
that are loaded at run-time.

cambridgehackers/klaatu-openal-soft,arkana-fts/openal-soft,alexxvk/openal-soft,mmozeiko/OpenAL-Soft,BeamNG/openal-soft,irungentoo/openal-soft-tox,rryan/openal-soft,franklixuefei/openal-soft,AerialX/openal-soft-android,Wemersive/openal-soft,jims/openal-soft,EddieRingle/openal-soft,arkana-fts/openal-soft,cambridgehackers/klaatu-openal-soft,rryan/openal-soft,franklixuefei/openal-soft,cambridgehackers/klaatu-openal-soft,mmozeiko/OpenAL-Soft,Wemersive/openal-soft,EddieRingle/openal-soft,irungentoo/openal-soft-tox,aaronmjacobs/openal-soft,alexxvk/openal-soft,dapetcu21/openal-soft,aaronmjacobs/openal-soft,BeamNG/openal-soft,jims/openal-soft