bp2build: cc_object converter.

This CL introduces a basic bp2build converter for cc_object modules.
cc_objects maps cleanly to cc_library targets, but with -fnoaddrsig.

This CL also demonstrates generating include deps within a macro to
allow the cc_object compilation to depend on a relative-include header
within an include dir.

e.g. if "foo.cc" includes "android/log.h" and the latter is located at
"include/android/log.h", the autogenerated header deps would export
"android/log.h" correctly to the foo.cc upstream target.

Test: GENERATE_BAZEL_FILES=true m nothing && bp2build-sync write && bazel build //bionic/libc:crtbegin_so1

Change-Id: Ifd9e097051ec184ab0a1929d07918f0ff4f24d98