Please give a chance to to use a specific pg_config while in compiling

[Killian Q. Zhuo]

This is a trivial change so I didn't fork the repo to file a PR for such a little update, I just paste the patch here.

The patch: http://paste.debian.net/plainh/6a9f193f

Please consider applying it by:

curl http://paste.debian.net/plainh/6a9f193f -o xxx.patch
git am xxx.patch

Thanks.

[Killian Q. Zhuo]

0001-give-a-chance-to-use-a-specific-pg_config-in-compili.patch.txt

Patch attached.

[Jov]

done by c7356e0
thanks！