Transform paths to headers in include dirs to take package boundaries into account.

This allows the following cc_library_static targets to build with bp2build:

- libc_freebsd
- libc_freebsd_large_stack
- libc_openbsd_ndk
- libc_gdtoa  (* but still fails for mixed builds)
- libc_aeabi
- libc_static_dispatch
- libc_dynamic_dispatch

This also allows a number of other cc_library_static targets to progress further in their builds.

Test: Added unit test
Test: bp2build-sync.py write; bazel build //bionic/...

Change-Id: I71742565c16594448a41a6428a5c993171ec4cb4