Postgres ftp source is not real time

[JalexChen]

While we are checking for the postgres version on their github, which is real time, the link we use to build postgresql, ftp.postgresql.org, is not updated, which results in a failed build.

two options i can think of:

• we create from a source tarball that is available with the announcement of the release
• implement a check to see if the version is available for download at the ftp url