Switch vogar from toolchain=jdk to toolchain=dx

Switch vogar from toolchain=jdk to toolchain=dx because
the name is more meaningful in a world where javac
is used with different Android tools.

Bug: 67934307
Test: None
Change-Id: Ife0e16cdf02aea95fbc88f5861e3ce7de5c0f937
diff --git a/tools/run-libcore-tests.sh b/tools/run-libcore-tests.sh
index eecdd2f..ed3cf40 100755
--- a/tools/run-libcore-tests.sh
+++ b/tools/run-libcore-tests.sh
@@ -149,7 +149,7 @@
 if [[ $using_jack == "true" ]]; then
   vogar_args="$vogar_args --toolchain jack --language JO"
 else
-  vogar_args="$vogar_args --toolchain jdk --language CUR"
+  vogar_args="$vogar_args --toolchain dx --language CUR"
 fi
 
 # JIT settings.