A common scenario is adding vm arguments when running tests. While this can be accomplished by JTREG="VM_OPTIONS=-Xfoo", this is a lot to type for a common case. In the future, when gtest accepts vm arguments as well, a separate, similar but yet different GTEST="VM_OPTIONS=-Xfoo" would be needed.

A new "global" TEST_VM_OPTS=X should behave as if VM_OPTIONS=X were present on all applicable test framework option control variables.