Baseline: 3f93d377d036d773fd505a18e084425a00fb94ea

Important changes:

  - Experimental support for path mapping `CppCompile` actions can be
    enabled via
    `--modify_execution_info=CppCompile=+supports-path-mapping`.

This release contains contributions from many people at Google, as well as detailyang, Fabian Meumertzheim, Greg Roodt, hvd, Jason Schroeder, Laurent Le Brun, Simon Mavi Stewart, Xdng Yng.