[LyX/master] Cmake build: Start demanding at least version 5.1 if compiling with gcc

[Pavel Sanda]

On Thu, Oct 24, 2024 at 04:05:37PM +0200, Jean-Marc Lasgouttes wrote:
> It may be that we still compile with gcc 6, which has bits of C++17. I feel
> a bit lazy to check this, but I could in principle. I would say that we
> allow ourselves to use every C++17 feature and see afterward what compiler
> supports it (provided that it is not later than gcc 8). Is that a clear
> policy?
> 
> I just checked the status, it seems that we need gcc 7 for <any>.
> https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.2017
> 
> What about requiring gcc 7?

I thought that distros which have GCC<8 do not ship qt5, but qt4.
Am I wrong here? Otherwise how are you going even to test it?

Pavel