ftpmirror.gnu.org in GNU_SOURCE seemingly broken - ftp.gnu.org works

[CJCShadowsan]

          > Holy thread revival Batman!

It appears that whilst building easyconfigs/n/ncurses/ncurses-6.5-GCCcore-13.3.0.eb - It attempts to download from https://ftpmirror.gnu.org/gnu/ncurses/ncurses-6.5.tar.gz which fails repeatedly...

...Downloading from https://ftp.gnu.org/gnu/ncurses/ncurses-6.5.tar.gz works first time.

Does this need changing now?

This also now breaks on easyconfigs/m/make/make-4.4.1-GCCcore-13.3.0.eb which tries to get make from: https://ftpmirror.gnu.org/gnu/make/make-4.4.1.tar.gz - Which also fails.

Originally posted by @CJCShadowsan in #4653 (comment)

[boegel]

@CJCShadowsan This may be highly dependent on which mirror you're hitting when ftpmirror is being used...

See also https://www.gnu.org/server/mirror.html, which mentions:

We recommend using this generic ftpmirror.gnu.org address wherever possible in links, documentation, etc., to reduce load on the main GNU server.

So using ftp.gnu.org instead would make us a bad citizen...