Copy implementation and header jars to make when possible

Fixes test issues caused by a jar containing a classes.dex file was
copied to a place that was expected a jar containing class files.

Bug: 191360201
Test: - in master-art
      find out/ -name \*core-icu4j\* | xargs rm -fr
      art/tools/buildbot-build.sh --target --installclean
      art/tools/bootjars.sh --path --core
      - examine file output from previous script for core-icu4j,
        before this change it contained classes.dex file after this
        change it contained *.class files.
Change-Id: I05ecf652535ec097125fb76d6ca80fee6587f98d