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
diff --git a/build/Android.common.mk b/build/Android.common.mk
index 5341136..b63d2dc 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -103,7 +103,7 @@
 
 ifeq ($(ART_USE_OPTIMIZING_COMPILER),true)
 DEX2OAT_FLAGS := --compiler-backend=Optimizing
-DALVIKVM_FLAGS := -Xcompiler-option --compiler-backend=Optimizing
+DALVIKVM_FLAGS += -Xcompiler-option --compiler-backend=Optimizing
 endif
 
 #