Direct Bazel builds from m.

This CL adds support to bp2build/Soong to dump a BUILD file under
out/soong/soong_injection/targets containing alias targets to their real
targets for every converted Soong module, regardless of whether they are
handcrafted or generated.

Test: TH
Change-Id: Ic1816fda5d019c395301618134fac68b3057d752