Add DALVIKVM_FLAGS to test invocation.

Now, only gtest don't use these flags.

Running tests with GC options e.g:
DALVIK_VM="-Xgc:GSS" mm test-art-host-oat

Added a --runtime-option to test/run-test which passes the args to
the test:
test/run-test --runtime-option -Xgc:GSS --runtime-option -XX:UseTLAB 080

Change-Id: Ic928df32cb5aa36d3b0b55456e8b535e82ee9e97