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>
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 601ca8b..08ca08e 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -4,7 +4,7 @@
 # link vmlinux
 #
 # vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_INIT) and
-# $(KBUILD_VMLINUX_MAIN) and $(KBUILD_VMLINUX_LIBS). Most are built-in.o files
+# $(KBUILD_VMLINUX_MAIN) and $(KBUILD_VMLINUX_LIBS). Most are built-in.a files
 # from top-level directories in the kernel tree, others are specified in
 # arch/$(ARCH)/Makefile. Ordering when linking is important, and
 # $(KBUILD_VMLINUX_INIT) must be first. $(KBUILD_VMLINUX_LIBS) are archives
@@ -18,7 +18,7 @@
 #   |   +--< init/version.o + more
 #   |
 #   +--< $(KBUILD_VMLINUX_MAIN)
-#   |    +--< drivers/built-in.o mm/built-in.o + more
+#   |    +--< drivers/built-in.a mm/built-in.a + more
 #   |
 #   +--< $(KBUILD_VMLINUX_LIBS)
 #   |    +--< lib/lib.a + more
@@ -51,13 +51,13 @@
 #
 # Traditional incremental style of link does not require this step
 #
-# built-in.o output file
+# built-in.a output file
 #
 archive_builtin()
 {
-	info AR built-in.o
-	rm -f built-in.o;
-	${AR} rcsTP${KBUILD_ARFLAGS} built-in.o			\
+	info AR built-in.a
+	rm -f built-in.a;
+	${AR} rcsTP${KBUILD_ARFLAGS} built-in.a			\
 				${KBUILD_VMLINUX_INIT}		\
 				${KBUILD_VMLINUX_MAIN}
 }
@@ -69,7 +69,7 @@
 	local objects
 
 	objects="--whole-archive				\
-		built-in.o					\
+		built-in.a					\
 		--no-whole-archive				\
 		--start-group					\
 		${KBUILD_VMLINUX_LIBS}				\
@@ -88,7 +88,7 @@
 
 	if [ "${SRCARCH}" != "um" ]; then
 		objects="--whole-archive			\
-			built-in.o				\
+			built-in.a				\
 			--no-whole-archive			\
 			--start-group				\
 			${KBUILD_VMLINUX_LIBS}			\
@@ -99,7 +99,7 @@
 			-T ${lds} ${objects}
 	else
 		objects="-Wl,--whole-archive			\
-			built-in.o				\
+			built-in.a				\
 			-Wl,--no-whole-archive			\
 			-Wl,--start-group			\
 			${KBUILD_VMLINUX_LIBS}			\
@@ -164,7 +164,7 @@
 	rm -f .tmp_System.map
 	rm -f .tmp_kallsyms*
 	rm -f .tmp_vmlinux*
-	rm -f built-in.o
+	rm -f built-in.a
 	rm -f System.map
 	rm -f vmlinux
 	rm -f vmlinux.o