Add bpf_test.go to build and fix tests

bpf_test.go was not listed in testSrcs, which meant it was not run
during the build, but ran and failed with go test android/soong/...

Don't redeclare the cc module types and mutators, use exported
functions from cc/testing.go instead, which contain a new
dependency needed by cc modules.

This reapplies I4542640e8ff08e71565ed50617dbe67d86b29b69 after
fixes for mac tests.

Test: m
Test: go test android/soong/...
Change-Id: I3dc3fdedbd7063df4a2e0cadf2a4e0711b1823ad