Call jack with -cp instead of -jar

Because the launcher does not support -jar.

Change-Id: I2dea7c65261f8fa508b81e758d4a901ab2e6dd90
diff --git a/tools/jack b/tools/jack
index bfe20fb..b1941a4 100755
--- a/tools/jack
+++ b/tools/jack
@@ -58,7 +58,7 @@
 # If not in server mode, exec jack
 #
 if [ "$SERVER" != "true" ]; then
-  exec $JACK_VM_COMMAND -jar $JACK_JAR "$@"
+  exec $JACK_VM_COMMAND -cp $JACK_JAR com.android.jack.Main "$@"
   echo "Cannot succeed to launch Jack" >&2
   exit 255
 fi