Use -target 8 for core-lambda-stubs

core-lambda-stubs is distributed as part of the SDK and should use
-target 8 for compatibility with old JDKs.

Bug: 150153790
Bug: 162522383
Test: javap -v --system none -bootclasspath "" -cp out/target/common/obj/JAVA_LIBRARIES/core-lambda-stubs_intermediates/classes.jar java.lang.invoke.LambdaMetafactory | grep "major version"
Change-Id: I73fcfefb353099fa6545b2ff1d2b2fcf677931ae
diff --git a/JavaLibrary.bp b/JavaLibrary.bp
index 0388a19..a383da7 100644
--- a/JavaLibrary.bp
+++ b/JavaLibrary.bp
@@ -373,6 +373,9 @@
         ":openjdk_lambda_stub_files",
         ":openjdk_lambda_duplicate_stub_files",
     ],
+    // This jar is packaged as part of the SDK, use -target 8 so that it works
+    // with old JDKs.
+    java_version: "1.8",
 }
 
 // An alternative to core-lambda-stubs that omits openjdk_lambda_duplicate_stub_files