Refactor build rules for libprofile-clang-*

Bug: http://b/194128476

Refactor build rules in toolchain-extras.  Reduce duplication before
adding a new variant of libprofile-clang-* for continuous coverage.

Test: verify libclang-* determinism
Change-Id: Id2bb24894c5b10053bb2a79efe1b78f6185a82d0
1 file changed