Change in coreboot[master]: tests: Enable config override for tests

[Jakub Czapiga (Code Review)]

Attention is currently required from: Julius Werner, Jan Dabros.
Jakub Czapiga has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52937 )

Change subject: tests: Enable config override for tests
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Patch Set 2:

(1 comment)

File tests/Makefile.inc:

https://review.coreboot.org/c/coreboot/+/52937/comment/7566b51c_ea63cfd8 
PS2, Line 89: $(TEST_KCONFIG_AUTOHEADER)
> The rule doesn't seem to have any inputs except the variables, so I don't think that dependency is n […]

It does not use file under path from this variable directly, but logically it does. Please correct me if I am wrong, but $(TEST_KCONFIG_AUTOHEADER) has to be executed to generate config and I think this is best place for it.