Change in coreboot[master]: $(TOP)/Makefile.inc: Handle the folder common before specific one

[Bao Zheng (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Martin Roth, Marshall Dawson, Paul Menzel, Julius Werner, Zheng Bao, Elyes Haouas, Felix Held.
Bao Zheng has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62750 )

Change subject: $(TOP)/Makefile.inc: Handle the folder common before specific one
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Patch Set 6:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/62750/comment/16c37d7b_f793f405 
PS3, Line 13: The duplicated "common" in the result string can be eliminated finally.
> yes. it doesn't remove duplication when creating Makefile.inc list. […]

all the Makefile.inc in "subdir" will be included as
-include path/Makefile.inc

“-include" means ignoring a makefile which does not exist
or cannot be remade. So it is ok to have a duplicated Makefile.inc.

includemakefiles= \
    $(foreach class,classes subdirs $(classes) $(special-classes), $(eval $(class)-y:=)) \
    $(info $(1)) \
    $(eval -include $(1)) \   <--- subdir Makefile.inc is included here
    $(foreach class,$(classes-y), $(call add-class,$(class))) \
    $(foreach special,$(special-classes), \
    	$(foreach item,$($(special)-y), $(call $(special)-handler,$(dir $(1)),$(item)))) \
    $(foreach class,$(classes), \
    	$(eval $(class)-srcs+= \
    		$$(subst $(absobj)/,$(obj)/, \
    		$$(subst $(top)/,, \
    		$$(abspath $$(subst $(dir $(1))/,/,$$(addprefix $(dir $(1)),$$($(class)-y)))))))) \
    $(eval subdirs+=$$(subst $(CURDIR)/,,$$(wildcard $$(abspath $$(addprefix $(dir $(1)),$$(subdirs-y))))))