Force protobuf to continue to use v51 (1.7) .class files

The default is changing to v52 (1.8).

The build for this package uses jarjar to repackage .class files.

The version of jarjar in the Android tree does not currently
support v52 .class files.

Bug: 26753820
(cherry picked from commit 8e67c67896e167937fd7b05493a57df5f4f7c90f)

Change-Id: I9cd43f3a45fab904a42ae2510623457a6aa941fb
diff --git a/Android.mk b/Android.mk
index d7e868a..8baffc2 100644
--- a/Android.mk
+++ b/Android.mk
@@ -172,6 +172,7 @@
 LOCAL_SRC_FILES := $(call all-java-files-under, java/src/main/java/com/google/protobuf/nano)
 LOCAL_SRC_FILES += $(call all-java-files-under, java/src/device/main/java/com/google/protobuf/nano)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_STATIC_JAVA_LIBRARY)
 
 # Java nano library (for host-side users)
@@ -183,6 +184,7 @@
 
 LOCAL_SRC_FILES := $(call all-java-files-under, java/src/main/java/com/google/protobuf/nano)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_HOST_JAVA_LIBRARY)
 
 # Java micro library (for device-side users)
@@ -195,6 +197,7 @@
 
 LOCAL_SRC_FILES := $(call all-java-files-under, java/src/main/java/com/google/protobuf/micro)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_STATIC_JAVA_LIBRARY)
 
 # Java micro library (for host-side users)
@@ -206,6 +209,7 @@
 
 LOCAL_SRC_FILES := $(call all-java-files-under, java/src/main/java/com/google/protobuf/micro)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_HOST_JAVA_LIBRARY)
 
 # Java lite library (for device-side users)
@@ -218,6 +222,7 @@
 
 LOCAL_SRC_FILES := $(JAVA_LITE_SRC_FILES)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_STATIC_JAVA_LIBRARY)
 
 # Java lite library (for host-side users)
@@ -229,6 +234,7 @@
 
 LOCAL_SRC_FILES := $(JAVA_LITE_SRC_FILES)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_HOST_JAVA_LIBRARY)
 
 # Java full library (for host-side users)
@@ -240,6 +246,7 @@
 
 LOCAL_SRC_FILES := $(JAVA_FULL_SRC_FILES)
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_HOST_JAVA_LIBRARY)
 
 # C++ lite library for the NDK.
@@ -547,6 +554,7 @@
         java_package = $(LOCAL_PATH)/src/google/protobuf/unittest_import_nano.proto|com.google.protobuf.nano, \
         java_outer_classname = $(LOCAL_PATH)/src/google/protobuf/unittest_import_nano.proto|UnittestImportNano
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_STATIC_JAVA_LIBRARY)
 
 # To test Android-specific nanoproto features.
@@ -592,6 +600,7 @@
         generate_intdefs = true, \
         store_unknown_fields = true
 
+LOCAL_JAVA_LANGUAGE_VERSION := 1.7
 include $(BUILD_STATIC_JAVA_LIBRARY)
 
 include $(CLEAR_VARS)