CI: run the tests in release mode for one configuration

[ogoffart]

Linux is tested both as stable and 1.64, so we can also change one of them to run in release to improve our coverage

Basically a test for #1993

[ogoffart]

Good idea. Fingers crossed it works and won't take too long :)

Of course it did not work because the fix for #1993 where not included. 🤦‍

Anyway, will rebase

[ogoffart]

The release build seems to take a very long time

[ogoffart]

For the release job:

> Build                  42m 46s
> Run tests          1h 15m 45s

For a debug build, it is about 8 and 13 minutes

[tronical]

Hmm maybe it could be a nightly CI run?

[ogoffart]

(note that these number are with a cold cache, maybe with a warm cache it would be faster)

maybe it could be a nightly CI run?

Yeah, we could try to reduce the amount of combination in our normal CI, and have a nightly CI that test more combination