Summary

Build "Updated documentation to be in line with moving MXE gcc to version 11 + libbacktrace"

Purpose of change

I noticed a couple of PRs got merged today, #52023 and #51997.

• Build from custom MXE GCC 11 #52023 - looks to move the internal build/test process to MXE gcc 11 so contributors should probably be instructed to the same version.
• Enable backtrace in MinGW release #51997 - looks to add libbacktrace to the internal build process, so the documentation was updated with instructions on how to do that.

Describe the solution

All modification of documentation only. Also only in relation to MXE (MingW).

• instructions for downloading and installing libbacktrace.
• Tweaked the gcc version for mxe to build.
• Altered compiler supported (MingW) to target 11.2 instead of 9.3.
• Removed the flag unsets for PCH and LIBBACKTRACE as new instructions support those flags being enabled when building C:DDA.
• Added a hint to rebuild mxe if potential contributors had previously built MXE.

Describe alternatives you've considered

Done nothing...
Leave out the hint that people may need to clean and rebuild their MXE to get gcc11.

Testing

Rebuilt MXE with the changed line.
Tested out the download and extraction commands.
Built x64 windows C:DDA and ran it on windows, seemed to work fine.

Did NOT test 32 bit builds... I'm a bit constrained at the moment and I can't do both (within reason).

Additional context

I only just started reading about workflows yesterday so I may have misinterpreted what the two referenced PRs did and thus my instructions are incorrect. My impression of workflows is something like a hybrid of shell script and makefile directives.

Some side stuff that could be of note:

• ncurses no longer builds for MXE, it was still building with MXE set to gcc5 and gcc9 but doesn't when set to gcc11. C:DDA documentation says (in remark) that ncurses for Windows being a non-starter, now looks even more correct.
• LTO flag set still fails to build.