Re: Warnings during make

> main.cc:641:23: warning: loop variable 'keyval' creates a copy from
> type 'const std::pair<std::__cxx11::basic_string<char>,
> std::__cxx11::basic_string<char> >' [-Wrange-loop-construct]
>   641 |       for (const auto keyval : init_scheme_variables_global)
>       |                       ^~~~~~
> main.cc:641:23: note: use reference type to prevent copying
>   641 |       for (const auto keyval : init_scheme_variables_global)
>       |                       ^~~~~~
>       |                       &

Thanks for the report.  The fixes suggested by the compiler are now
this MR.

  https://gitlab.com/lilypond/lilypond/-/merge_requests/2250


    Werner