Keep InstrumentationTestCase in main dex

They must be in main dex or InstrumentationTestRunner won't find them.

Bug: 31383194

Test: frameworks/base/core/tests/hosttests/test-apps/MultiDex*
Change-Id: I76ea9e9f46fa95f6a1f2d35410480be42f7a5151
diff --git a/library/jack-meta/legacyMultidexInstallation.jpp b/library/jack-meta/legacyMultidexInstallation.jpp
index 8a81eba..a5a7167 100644
--- a/library/jack-meta/legacyMultidexInstallation.jpp
+++ b/library/jack-meta/legacyMultidexInstallation.jpp
@@ -47,3 +47,10 @@
       method void attachBaseContext(class android.content.Context)
       ;
     }
+
+instrumentationTestCase:
+  @@com.android.jack.annotations.ForceInMainDex
+  class *
+    extends {
+      class android.test.InstrumentationTestCase
+    }