vm-config: Allow platforms to construct their own classpath arguments.

In particular, DalvikPlatform now uses "-Djava.class.path=$cp"
instead of "-cp $cp" which didn't work with the app_process custom vm.

This enables caliper to test/benchmark Android framework-dependent code
(e.g. any typical application code) without needing to depend on a
specific version of Android which has an updated app_process binary.

Bug: 32311997
Test: vogar --benchmark --mode app_process \

Change-Id: Iaa1d947ef785172f208d5175f0be83e55a12d04a
4 files changed