Instruct gdc to look for standard library in another directory

[Johann]

On Saturday, 1 July 2023 at 10:18:43 UTC, Iain Buclaw wrote:
> Is it too much to ask downstream package maintainers to 
> politely use `/usr/share/dlang/{ldc,dmd}` ? :-)

Thanks for your help, Iain. I am going to report a bug to the 
distro maintainers then.