Use instruction specific dalvik cache dirs.

- All oat & art files are now placed under /data/dalvik-cache/<isa>/.
- GetDalvikCacheOrDie now requires a mandatory subdirectory argument,
  and is implicitly rooted under /data/.
- Added helper methods to convert InstructionSet enums into strings
  and vice versa.

(cherry picked from commit 2974bc3d8a5d161d449dd66826d668d87bdc3cbe)

Change-Id: Ic7986938e6a7091a2af675ebafec768f7b5fb8cd
diff --git a/build/Android.gtest.mk b/build/Android.gtest.mk
index f25217f..429c523 100644
--- a/build/Android.gtest.mk
+++ b/build/Android.gtest.mk
@@ -49,6 +49,7 @@
 	runtime/gtest_test.cc \
 	runtime/indenter_test.cc \
 	runtime/indirect_reference_table_test.cc \
+	runtime/instruction_set_test.cc \
 	runtime/intern_table_test.cc \
 	runtime/leb128_test.cc \
 	runtime/mem_map_test.cc \