Add generic_check function and add new default check target to build.sh.

The check target is excluded from the all target since it can often take a
very long time to run.

build.sh.functions

@@ -18,7 +18,7 @@ all()
     for METHOD in $METHODS 
     do
         case $METHOD in
-             all*|*clean) ;;
+             all*|*clean|check) ;;
              *) $METHOD
                 ;;
         esac