No standard option to suppress output, use redirects.

build.sh

@@ -2,7 +2,7 @@
 
 # Check for all the stuff I need to function.
 for f in gcc flex bison mvn; do
-	which -s $f || ( echo "Required program $f is missing. Please install it and try again." ; exit 1 )
+	which $f > /dev/null 2>&1 || ( echo "Required program $f is missing. Please install it and try again." ; exit 1 )
 done
 
 (cd tpcds-gen; make)