kbuild: rename built-in.o to built-in.a

Incremental linking is gone, so rename built-in.o to built-in.a, which
is the usual extension for archive files.

This patch does two things, first is a simple search/replace:

git grep -l 'built-in\.o' | xargs sed -i 's/built-in\.o/built-in\.a/g'

The second is to invert nesting of nested text manipulations to avoid
filtering built-in.a out from libs-y2:

-libs-y2 := $(filter-out %.a, $(patsubst %/, %/built-in.a, $(libs-y)))
+libs-y2 := $(patsubst %/, %/built-in.a, $(filter-out %.a, $(libs-y)))

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Makefile.lib

@@ -27,7 +27,7 @@ modorder	:= $(patsubst %/,%/modules.order, $(filter %/, $(obj-y)) $(obj-m:.o=.ko
 
 # Handle objects in subdirs
 # ---------------------------------------------------------------------------
-# o if we encounter foo/ in $(obj-y), replace it by foo/built-in.o
+# o if we encounter foo/ in $(obj-y), replace it by foo/built-in.a
 #   and add the directory to the list of dirs to descend into: $(subdir-y)
 # o if we encounter foo/ in $(obj-m), remove it from $(obj-m)
 #   and add the directory to the list of dirs to descend into: $(subdir-m)
@@ -35,7 +35,7 @@ __subdir-y	:= $(patsubst %/,%,$(filter %/, $(obj-y)))
 subdir-y	+= $(__subdir-y)
 __subdir-m	:= $(patsubst %/,%,$(filter %/, $(obj-m)))
 subdir-m	+= $(__subdir-m)
-obj-y		:= $(patsubst %/, %/built-in.o, $(obj-y))
+obj-y		:= $(patsubst %/, %/built-in.a, $(obj-y))
 obj-m		:= $(filter-out %/, $(obj-m))
 
 # Subdirectories we need to descend into
@@ -54,7 +54,7 @@ multi-objs-m := $(foreach m, $(multi-used-m), $($(m:.o=-objs)) $($(m:.o=-y)))
 
 # $(subdir-obj-y) is the list of objects in $(obj-y) which uses dir/ to
 # tell kbuild to descend
-subdir-obj-y := $(filter %/built-in.o, $(obj-y))
+subdir-obj-y := $(filter %/built-in.a, $(obj-y))
 
 # Replace multi-part objects by their individual parts, look at local dir only
 real-objs-y := $(foreach m, $(filter-out $(subdir-obj-y), $(obj-y)), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))),$($(m:.o=-objs)) $($(m:.o=-y)),$(m)))