[M] Change in coreboot[main]: Makefile.mk: Add a common link_stage function and use it

[Arthur Heymans (Code Review)]

Attention is currently required from: Julius Werner, Jérémy Compostella, Nico Huber, Philipp Hug, Ron Minnich.

Arthur Heymans has posted comments on this change by Arthur Heymans. ( https://review.coreboot.org/c/coreboot/+/83574?usp=email )

Change subject: Makefile.mk: Add a common link_stage function and use it
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Patch Set 2:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/83574/comment/f4f45fa8_17137a5b?usp... :
PS2, Line 16: - the x86 --oformat is dropped as it is not needed.
> Would be nice to do this in smaller steps, e.g. one patch to drop --oformat,
> one to drop LIBGCC_FILE_NAME_ (this one looks like a merge artifact after
> switching to COMPILER_RT_ in November 2014 oO).
>
> And now I just realized why we don't need the `--oformat`. It's because we
> use separate toolchains now? i.e. the x86_64 one doesn't support i386 any
> more. But wouldn't this break compiling with a host toolchain?

I think defining the format in the linker script would be a clean solution to that.