Add core-ojtests target to host build and to vogar classpath

This CL adds support of running ojtests (TestNG based) using vogar.
Now run-libcore-tests.sh should be able to run all unit tests including
TestNg ones from upstream.

Bug: 208639267
Test: art/tools/run-libcore-tests.sh --mode host \
      test.java.lang.String.IsBlank
Change-Id: Id842fe5a078b127229380855ce2a60815c560578
2 files changed