Add apex name to description

Otherwise we see multiple concurrent builds of different actions with
the same description:

    0:09 //external/fmtlib:fmtlib clang++ src/format.cc
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc

Is now:

    0:09 //external/fmtlib:fmtlib clang++ src/format.cc
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc [com.android.resolv]
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc [com.android.adbd]
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc [com.android.art.debug]
    0:09 //external/fmtlib:fmtlib clang++ src/format.cc [com.android.media]

Test: m  <watch output>
Change-Id: Ib8fccc144e8fe5fc33cafe8536538b892bd42765