Add custom CC wrapper to the wrapper whitelist

[hodrob84]

Some toolchains use custom (or at least not widely used) CC wrappers, and passes that through the CC env var before the compiler, like:

CC = <custom_wrapper> -gcc

Add support to CC_KNOWN_WRAPPER_CUSTOM env var, to be able to extend the 'known_wrappers' list with this <custom_wrapper>, and handle these special cases.

[NobodyXu]

Thanks for the PR!

Can you please list some of the wrappers used?

If it is often used we can just add to our pre-defined list.

[hodrob84]

This is 'ucfront-gcc' in my case. I just wanted to avoid to pollute it with a less commonly used one, and add something to make it easier to fit to one's purpose.

[NobodyXu]

Thanks, is passing CC=ucfront-gcc not enough?

I.e., our compiler detection doesn't work?

If the compiler detection doesn't work for ucfront-gcc, then I think we should fix the detection logic instead.

AFAIK ucfront-gcc in debian usually means gcc for a specific target/libc or other config, so it should have the same kinds of behavior as gcc.

[hodrob84]

Sorry, I wasn't clear. That's just the wrapper. The passed CC is:
CC=ucfront-gcc <arch>-gcc

[NobodyXu]

In this case, I does think it makes sense.

Cc @thomcc does it LGTY?

[thomcc]

I don't see a problem with this.

[NobodyXu]

Thanks, I'll merge it in then