Ongoing fixes and improvements, transient suppressor is gone. Also,
dropping isac because it doesn't seem to be useful, and is just build
system deadweight now.
Upstream references:
Version: 131.0.6778.200
WebRTC: 79aff54b0fa9238ce3518dd9eaf9610cd6f22e82
Chromium: 2a19506ad24af755f2a215a4c61f775393e0db42
Too much information was specified manually. All this is deduced
automatically if you specify the library as the first positional
argument.
Only absl_base needs to be in Requires: because absl_optional's header
file is needed at build time.
Also add a check in the CI for the pc files being usable.
