Make bsd.linker.mk work with the MacOS linker

[arichardson]

Summary

This is not strictly required for crossbuilding but having lots of warnings
from bsd.linker.mk in the output was making it hard to see the actual
warning messages.

[imp]

share/mk/bsd.linker.mk

69

Were it not for the weird exit value, you could do this more simply as ld <blah> --version || ld <blah> -v || echo none.

I'm surprised that 'head' results in an exit of 141 though. Is head returning that?

[arichardson]

share/mk/bsd.linker.mk

69

LD can print more than one line and head exits after the first line has been printed so it dies with a pipe closed error.

This is only a problem when changing the bmake shell to use -o pipefail, so I can remove it if you prefer.

[arichardson]

simplify and rebase

[emaste]

Is there anything we'd do differently based on mac linker version?

[arichardson]

In D14318#577027, @emaste wrote:

Is there anything we'd do differently based on mac linker version?

I doubt the version matters, but we could avoid adding ld.bfd/ld.lld specific flags during bootstrapping.
There currently aren't any, but that might change (and silencing the warnings is quite useful).

[emaste]

In D14318#577057, @arichardson wrote:

I doubt the version matters, but we could avoid adding ld.bfd/ld.lld specific flags during bootstrapping.
There currently aren't any, but that might change (and silencing the warnings is quite useful).

Yeah, it's specifically the version I'm wondering about, although I suppose it would be just as strange to detect macos linker and use a fake version (e.g. 0.0.0)

[imp]

This version looks good to me.