Ignore enviroment variables which aren't supported

[Freed-Wu]

By default, nix-shell will enter a shell and

export AS=as
export LD=ld

However, xmake cannot work. Why not ignore them and use default value then give a warning?

[waruqi]

We won't ignore it

[Freed-Wu]

I means when they cannot work, ignore them and use default to make it work.

[waruqi]

xmake will read the toolchain configuration from $CC $LD. This is the normal default behavior of xmake, but xmake cannot control how users and systems set them.

[waruqi]

This is a nix issue, xmake cannot distinguish whether the user intentionally sets LD=ld.

[Freed-Wu]

Although xmake doesn't know if LD=ld is set by user, it know LD=ld is not supported. Just print a warning and ignore it, then use default LD to link, which will be a better user exprience.

[waruqi]

No, LD=ld is supported, it depends on the purpose of the user project. If it is for some os kernel projects, users will set LD=ld to do more customized linking work.

https://github.com/xmake-io/xmake/blob/dev/xmake/modules/core/tools/ld.lua

and ld.lld, ld64.lld, lld.link are also supported.

Just for common c/c++ projects, xmake will use g++/clang++ instead of ld by default. if use ld, you need to configure -lc++ and more links flags by yourself.

But xmake cannot distinguish the actual purpose of the user project, which requires the user to distinguish and set the correct LD to xmake.