Use homogeneous space compaction if proper flag is set.

If the flag ART_USE_HSPACE_COMPACT is set then we use
hspace compaction.

Bug: 16401001

Change-Id: I74e1db764f9ff16c007fa3bd16cb2c9b468ec83c
diff --git a/runtime/Android.mk b/runtime/Android.mk
index 09ec004..bdecc7e 100644
--- a/runtime/Android.mk
+++ b/runtime/Android.mk
@@ -325,6 +325,10 @@
   LIBART_CFLAGS += -DUSE_JEMALLOC
 endif
 
+ifeq ($(ART_USE_HSPACE_COMPACT),true)
+  LIBART_CFLAGS += -DART_USE_HSPACE_COMPACT
+endif
+
 # $(1): target or host
 # $(2): ndebug or debug
 define build-libart