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

[Nico Huber (Code Review)]

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

Nico Huber 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/8cf0f144_a3d38121?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, […]

How would that look like? it's not just one linker script, right?

Actually, it feels like this is xcompile's job.