Add legacy-test as replacement for core-junit

Statically includes core-junit-static into legacy-test target so
that legacy-test can be used in place of core-test. Once that
switch over has been done then android.test classes that are
being removed from the public API can be safely moved into here.

Bug: 30188076
Test: make legacy-test and check contents of generated legacy-test artifacts

Change-Id: I75488303067c4ac34c46279bfce9a51273adcc34
diff --git a/Android.mk b/Android.mk
index db5dd01..cdb3834 100644
--- a/Android.mk
+++ b/Android.mk
@@ -494,7 +494,7 @@
 LOCAL_ADDITIONAL_DEPENDENCIES := $(framework_res_R_stamp)
 
 LOCAL_NO_STANDARD_LIBRARIES := true
-LOCAL_JAVA_LIBRARIES := core-oj core-libart conscrypt okhttp core-junit bouncycastle ext
+LOCAL_JAVA_LIBRARIES := core-oj core-libart conscrypt okhttp legacy-test bouncycastle ext
 LOCAL_STATIC_JAVA_LIBRARIES := framework-protos
 
 LOCAL_MODULE := framework