bug#40459: Non-reproducible behaviour in libtool < 2.2.7b bootstrapped ltmain.sh

[Carl Dong]

Hi Guix!

While investigating a libstdc++.a reproducibility issue, I found that libtool 
prior to 74c8993c (first included in version 2.2.7b, link: 
https://git.savannah.gnu.org/cgit/libtool.git/commit/?id=74c8993c178a1386ea5e2363a01d919738402f30)
 did not sort find output. It seems that many packages (including all released 
gcc versions so far) are bootstrapped with a libtool < 2.2.7b.

There are probably many ways to approach this, and I propose that we could 
simply use a somewhat strict regex find and replace on ltmain.sh.

Would love feedback and better ideas!

Cheers,
Carl Dong