Update Starlark to create `build_target` and `build_for`#905

Merged

cgrindel merged 3 commits intomainfrom

cg/gh573_starlark_build_target_new

Aug 11, 2022

Commits on Aug 10, 2022

Add Starlark functions to create build target and build_for
cgrindel
committed
Add build_action to tools/generator scheme. Fixed some failures
cgrindel
committed
Tests green passing along custom build_target in tools/generator.
cgrindel
committed