Add options for building/testing with coverage.

    acov --clean
    mm -B NATIVE_COVERAGE=true ART_COVERAGE=true test-art-host
    acov --host

-B is needed because you need to be sure you rebuild *all* of ART with
coverage.

Change-Id: Ib94ef610bd1b44dc45624877710ed733051b7a50
diff --git a/disassembler/Android.mk b/disassembler/Android.mk
index 735c850..c9aa8c8 100644
--- a/disassembler/Android.mk
+++ b/disassembler/Android.mk
@@ -84,6 +84,7 @@
 
   LOCAL_ADDITIONAL_DEPENDENCIES := art/build/Android.common_build.mk
   LOCAL_ADDITIONAL_DEPENDENCIES += $(LOCAL_PATH)/Android.mk
+  LOCAL_NATIVE_COVERAGE := $(ART_COVERAGE)
   # For disassembler_arm64.
   ifeq ($$(art_ndebug_or_debug),debug)
      LOCAL_SHARED_LIBRARIES += libvixld