Change in coreboot[master]: payloads/tianocore: Fix compilation for UEFIPAYLOAD option

[Matt DeVillier (Code Review)]

Attention is currently required from: Martin Roth, Stefan Reinauer, Angel Pons.
Matt DeVillier has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52191 )

Change subject: payloads/tianocore: Fix compilation for UEFIPAYLOAD option
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Patch Set 1:

(1 comment)

File payloads/external/tianocore/Makefile:

https://review.coreboot.org/c/coreboot/+/52191/comment/767c0baf_756c9f36 
PS1, Line 49: ARCH=-a IA32 -a X64 -p UefiPayloadPkg/UefiPayloadPkg.dsc
> I'd add a `dsc_file` variable that gets set accordingly for CorebootPayloadPkg and UefiPayloadPkg

but that's arch dependent, and what does setting another variable really accomplish when it's only used one place?