RFC: Increasing minimum gcc & clang versions

[MikePopoloski]

I'd like to increase the minimum required GCC version to 13 and clang to 19 for the next release. These are supported by the previous Ubuntu LTS release (24.04) and RHEL has corresponding toolset packages so this is hopefully not too onerous., but I'm opening this RFC to allow downstream users to express opinions. Tagging @povik and @fabianschuiki but others should feel free to chime in as well.

I'd like to also eventually enable C++23 support, but for now we'll start with the compiler bump.

[povik]

I think that is fine for yosys-slang. I'm also checking internally because of our plans to link slang into openroad but it seems to be doable. We do support Debian 12 and will continue to do so for a while so we would need to use a non-default compiler there.

[fabianschuiki]

Let me bring it up in this week's CIRCT open design meeting. We treat Verilog frontend support as an optional feature, and we already require users to have a Slang-compatible compiler in case they want to opt-in. So this might not be too big of an issue.