tree 243033be0531c709a8182c154707877cdb19b364
parent 262181b8370b3049dfb6f584dfaef4039f927517
author gregce <gregce@google.com> 1575406695 -0800
committer Copybara-Service <copybara-worker@google.com> 1575406756 -0800

Fix action conflict errors from exec config / targetLibcTop mismatch.

Summary:

 1. `host.targetLibcTopLabel = libcTopLabel` creates action conflicts with
    exec configs.
 2. This is because a top-level exec config inherits a different libcTopLabel than
    one after, say, an Android split transition.
 3. This doesn't break host configs since they all inherit the (pre-transition)
    top-level config.
 4. Since the intention of targetLibcTopLabel is to preserve the top-level config
    for a temporary C++ toolchain hack, I've updated its semantics to guarantee that
    more forcefully.
PiperOrigin-RevId: 283604079