kmsaudiomixerbin: Remove unused variables

Change-Id: I0af0fdfe465b7214b3b5243b14fac07d16aa91c9
Remove unused variables in tests

Change-Id: I967fb7b8143a7813c06d3e73a791ff85615783ca
cmake: Process warnings as errors

Change-Id: I05be06b5a4ec713ccf12a5671fc979b7eda3b8af
cmake: Remove use of c99 standard in plugin compilation

Change-Id: Iea9046e715f44604a78e4838a089bfd9766f8ef5