Add downloadMappingFilesForRetraceTests as a test-dependency

Bug: 132850880
Change-Id: I7f789dc8b3e3eb803e089307c371ce0aa65cb968
diff --git a/build.gradle b/build.gradle
index 87bae70..ac517a1 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1961,6 +1961,7 @@
                     "Art only runs on Linux and tests requiring Art will be skipped")
         }
         dependsOn downloadDeps
+        dependsOn downloadMappingFilesForRetraceTests
         dependsOn buildExamples
         dependsOn buildExamplesKotlin
         dependsOn buildKotlinR8TestResources