Fix Ubuntu 25.10 install failures by pinning Linux builds to GNU17

[JWiker]

No description provided.

[gighen74]

I tested the workaround suggested and seems to work. In details:

1. In a test bench of RST 5.1.1 I modified the three make files in build/make as suggested;
2. I set gcc 15 as the default compiler;
3. I launched the RST code compilation.

it worked!

Gigi

[JWiker]

@ksterne what's the official procedure to get this merged back into main?

[ksterne]

@JWiker, it's best to point this to develop . We could elevate this to a patch release if there's more Ubuntu 25 users. It not being a LTS release, I'm hesitant to do make a patch release. We should look at requirements for Ubuntu 26 (release due later this month) installation and update where it's needed.