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

	configuration.

	Kbuild compiles all the $(obj-y) files.  It then calls

	"$(AR) rcSTP" to merge these files into one built-in.o file.

	"$(AR) rcSTP" to merge these files into one built-in.a file.

	This is a thin archive without a symbol table, which makes it

	unsuitable as a linker input.

	The scripts/link-vmlinux.sh script later makes an aggregate

	built-in.o with "${AR} rcsTP", which creates the thin archive

	built-in.a with "${AR} rcsTP", which creates the thin archive

	with a symbol table and an index, making it a valid input for

	the final vmlinux link passes.

	The order of files in $(obj-y) is significant.  Duplicates in

	the lists are allowed: the first instance will be linked into

	built-in.o and succeeding instances will be ignored.

	built-in.a and succeeding instances will be ignored.

	Link order is significant, because certain functions

	(module_init() / __initcall) will be called during boot in the

	Note: Of course, when you are building objects into the kernel,

	the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,

	kbuild will build an ext2.o file for you out of the individual

	parts and then link this into built-in.o, as you would expect.

	parts and then link this into built-in.a, as you would expect.

--- 3.4 Objects which export symbols

--- 3.5 Library file goals - lib-y

	Objects listed with obj-* are used for modules, or

	combined in a built-in.o for that specific directory.

	combined in a built-in.a for that specific directory.

	There is also the possibility to list objects that will

	be included in a library, lib.a.

	All objects listed with lib-y are combined in a single

	Note that the same kbuild makefile may list files to be built-in

	and to be part of a library. Therefore the same directory

	may contain both a built-in.o and a lib.a file.

	may contain both a built-in.a and a lib.a file.

	Example:

		#arch/x86/lib/Makefile

	$(head-y) lists objects to be linked first in vmlinux.

	$(libs-y) lists directories where a lib.a archive can be located.

	The rest list directories where a built-in.o object file can be

	The rest list directories where a built-in.a object file can be

	located.

	$(init-y) objects will be located after $(head-y).

		extra-y := head.o init_task.o

	In this example, extra-y is used to list object files that

	shall be built, but shall not be linked as part of built-in.o.

	shall be built, but shall not be linked as part of built-in.a.

--- 6.7 Commands useful for building a boot image

--------

The build system has, as of 4.13, switched to using thin archives (`ar T`)

rather than incremental linking (`ld -r`) for built-in.o intermediate steps.

rather than incremental linking (`ld -r`) for built-in.a intermediate steps.

This requires binutils 2.20 or newer.

Flex

# Most importantly: sub-Makefiles should only ever modify files in

# their own directory. If in some directory we have a dependency on

# a file in another dir (which doesn't happen often, but it's often

# unavoidable when linking the built-in.o targets which finally

# unavoidable when linking the built-in.a targets which finally

# turn into vmlinux), we will call a sub make in that other dir, and

# after that we are sure that everything which is in that other dir

# is now up to date.

vmlinux-alldirs	:= $(sort $(vmlinux-dirs) $(patsubst %/,%,$(filter %/, \

		     $(init-) $(core-) $(drivers-) $(net-) $(libs-) $(virt-))))

init-y		:= $(patsubst %/, %/built-in.o, $(init-y))

core-y		:= $(patsubst %/, %/built-in.o, $(core-y))

drivers-y	:= $(patsubst %/, %/built-in.o, $(drivers-y))

net-y		:= $(patsubst %/, %/built-in.o, $(net-y))

init-y		:= $(patsubst %/, %/built-in.a, $(init-y))

core-y		:= $(patsubst %/, %/built-in.a, $(core-y))

drivers-y	:= $(patsubst %/, %/built-in.a, $(drivers-y))

net-y		:= $(patsubst %/, %/built-in.a, $(net-y))

libs-y1		:= $(patsubst %/, %/lib.a, $(libs-y))

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

virt-y		:= $(patsubst %/, %/built-in.o, $(virt-y))

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

virt-y		:= $(patsubst %/, %/built-in.a, $(virt-y))

# Externally visible symbols (used by link-vmlinux.sh)

export KBUILD_VMLINUX_INIT := $(head-y) $(init-y)

/*

 * Because string functions are both inline and exported functions and

 * folder arch/blackfin/lib is configured as a library path in Makefile,

 * symbols exported in folder lib  is not linked into built-in.o but

 * symbols exported in folder lib  is not linked into built-in.a but

 * inlined only. In order to export string symbols to kernel module

 * properly, they should be exported here.

 */

	$(call cmd,systbl_chk)

ifeq ($(CONFIG_PPC_OF_BOOT_TRAMPOLINE),y)

$(obj)/built-in.o:		prom_init_check

$(obj)/built-in.a:		prom_init_check

quiet_cmd_prom_init_check = CALL    $<

      cmd_prom_init_check = $(CONFIG_SHELL) $< "$(NM)" "$(obj)/prom_init.o"