Pin libraries needed by vogar tool to java 1.7

vogar still uses javac/dx by default. dx does not
handle v52 class files. The default java version
is going to switch to 1.8. This change pins the
targets need by vogar to 1.7.

Bug: 26753820
Bug: 27310428
Change-Id: Ie06378b11acd2a96daf6ddd0f38ab2a90bcc9a88
diff --git a/Android.mk b/Android.mk
index 2e03c2b..7c6cfd9 100644
--- a/Android.mk
+++ b/Android.mk
@@ -28,5 +28,6 @@
 LOCAL_SRC_FILES := $(call all-java-files-under, guava/src)
 LOCAL_MODULE := guavalib
 LOCAL_STATIC_JAVA_LIBRARIES := jsr305lib
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 
 include $(BUILD_HOST_JAVA_LIBRARY)