Moves to specifying attributes as a map, such at it is possible to add
additional attributes conditionally. This is in particular useful once
supporting the `enabled` property which will add
`target_compatible_with`
Test: go test soong tests
Change-Id: Iade8eed1ce3acb1d1712a9ee3119d9ae59675624
For cc_binary, changing the handling of version_script to no longer be a
LabelAttribute, which reduces test coverage of that type. Expand
prebuilt_etc to handle arch-variant srcs and correct a bug in
LabelAttribute.
Test: build/bazel/ci/bp2build.sh
Change-Id: I620bc3a43b28c1873f335e30099844ca79ce94c1
