Build build/libs/jdwp-tests-preN-dex.jar

The target to build this jar was added in commit
74143163 ("Use prebuilt dex version of JDWP in debug tests.", 2017-11-24),
Ib671fc6d17f7ed193bd8cc13d10b983530a5fd4f,
but it was not added as a dependency in Gradle.

We did not have any test failures until DexInspector usage was added in
85a33fe3 ("CF backend: Implement minification", 2018-03-22),
I81b18fbd224bce5bb3ecb4bb08a6843975408f85.

Build the file since future debugging tests might need it.

Change-Id: I6e3ca3caa6d82f50a7a3f9d03ff34c8cb707d94b
diff --git a/build.gradle b/build.gradle
index a7c2127..8237781 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1453,6 +1453,7 @@
         dependsOn jctfTestsClasses
         dependsOn buildDebugInfoExamplesDex
         dependsOn buildPreNJdwpTestsJar
+        dependsOn buildPreNJdwpTestsDex
     } else {
         logger.lifecycle("WARNING: Testing in not supported on your platform. Testing is only fully supported on " +
             "Linux and partially supported on Mac OS and Windows. Art does not run on other platforms.")