Fix to_jetty.sh initialization order

The output directory must exist in order to cd into it and run
pwd to locate its contents on disk.

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/to_jetty.sh b/to_jetty.sh
index b41d5b7..832ea6c 100755
--- a/to_jetty.sh
+++ b/to_jetty.sh
@@ -14,11 +14,11 @@
 	exit 1
 fi
 
+(cd appdist && mvn clean install) &&
+
 out=$(cd appdist/target/gerrit-*-bin.dir/gerrit-* && pwd) &&
 ctx="$jetty/contexts/gerrit.xml" &&
 
-(cd appdist && mvn clean install) &&
-
 cp $out/www/gerrit-*.war "$jetty/webapps/gerrit.war" &&
 
 if [ -f "$ctx" ]