Prepare for removal of legacy-test from default targets

In preparation for removing junit classes from the Android API
the legacy-test target will be removed from the
TARGET_DEFAULT_JAVA_LIBRARIES. This change adds explicit
dependencies on junit and/or legacy-android-test to ensure that
modules will compile properly once it is removed.

Bug: 30188076
Test: make checkbuild
Change-Id: I4054b3aee15ebbb319e57363d5c56fda956afbec
diff --git a/tests/Android.mk b/tests/Android.mk
index bb3bd18..b0d3c22 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -4,6 +4,7 @@
 LOCAL_MODULE_TAGS := tests
 
 LOCAL_JAVA_LIBRARIES := android.test.runner
+LOCAL_STATIC_JAVA_LIBRARIES := junit legacy-android-test
 
 LOCAL_SRC_FILES := $(call all-java-files-under, src)