Enable bootstrap tests for 12.0.0

Bug: 337801526
Change-Id: Iaa431f8132d538d1d6e98b433e2acb7384c737c1
diff --git a/d8_r8/test/build.gradle.kts b/d8_r8/test/build.gradle.kts
index c26b6d8..5cf352f 100644
--- a/d8_r8/test/build.gradle.kts
+++ b/d8_r8/test/build.gradle.kts
@@ -58,7 +58,7 @@
 
   // TODO(b/337801526): Enable for all runtimes
   fun runBootstrapTests() : Boolean {
-    val enabled = listOf("dex-default", "dex-8.1.0", "dex-13.0.0")
+    val enabled = listOf("dex-default", "dex-8.1.0", "dex-13.0.0", "dex-12.0.0")
     if (project.hasProperty("runtimes")) {
       for (doRun : String in enabled) {
         if (project.property("runtimes").toString().contains(doRun)) {