build.sh: commit JOBS=1 for nightly

This has already been the case in production for quite a while,
so just formalizing this for nightly (already used for longer on lts)

There are too frequent load collisions between heavy packages otherwise:
unfortunately the non-parallel-builds section has no effect with curator2

automated/build.sh

@@ -121,7 +121,7 @@ docker run $ARGS_PREBUILD $IMAGE /bin/bash -c 'GHCVER=$(sed -n "s/^ghc-version:
 
 case $SHORTNAME in
     lts) JOBS=1 ;;
-    nightly) JOBS=2 ;;
+    nightly) JOBS=1 ;;
 esac
 
 # Now do the actual build. We need to first set the owner of the home directory