Add new files appearing in SPIRV-Tools to Android.mk.
diff --git a/third_party/Android.mk b/third_party/Android.mk
index 3d97944..153a961 100644
--- a/third_party/Android.mk
+++ b/third_party/Android.mk
@@ -123,11 +123,12 @@
 		source/operand.cpp \
 		source/print.cpp \
 		source/spirv_endian.cpp \
+		source/spirv_target_env.cpp \
 		source/table.cpp \
 		source/text.cpp \
 		source/text_handler.cpp \
-		source/validate_cfg.cpp \
 		source/validate.cpp \
+		source/validate_cfg.cpp \
 		source/validate_id.cpp \
 		source/validate_instruction.cpp \
 		source/validate_layout.cpp \