[XS] Change in coreboot[main]: Makefile: Fix no-op incremental build

[Raul Rangel (Code Review)]

Attention is currently required from: Martin L Roth, Nicholas Chin.

Raul Rangel has posted comments on this change by Nicholas Chin. ( https://review.coreboot.org/c/coreboot/+/84385?usp=email )

The change is no longer submittable: All-Comments-Resolved is unsatisfied now.

Change subject: Makefile: Fix no-op incremental build
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Patch Set 2:

(2 comments)

File Makefile:

https://review.coreboot.org/c/coreboot/+/84385/comment/26c387b8_5a43aecc?usp... :
PS2, Line 232: # Fix for no-op build
Add a more descriptive comment on why this is needed.

https://review.coreboot.org/c/coreboot/+/84385/comment/e35a736a_5f99ffc2?usp... :
PS2, Line 233: $(objutil)/kconfig/conf
Can we just add this as a top-level target:
```
real-all: $(objutil)/kconfig/conf
```