sh: boot: avoid unneeded rebuilds under arch/sh/boot/compressed/

Even if none of source code is updated, the following are every time
rebuilt:

CC arch/sh/boot/compressed/cache.o
SHIPPED arch/sh/boot/compressed/ashiftrt.S
AS arch/sh/boot/compressed/ashiftrt.o
SHIPPED arch/sh/boot/compressed/ashldi3.c
CC arch/sh/boot/compressed/ashldi3.o
SHIPPED arch/sh/boot/compressed/ashrsi3.S
AS arch/sh/boot/compressed/ashrsi3.o
SHIPPED arch/sh/boot/compressed/ashlsi3.S
AS arch/sh/boot/compressed/ashlsi3.o
SHIPPED arch/sh/boot/compressed/lshrsi3.S
AS arch/sh/boot/compressed/lshrsi3.o
LD arch/sh/boot/compressed/vmlinux
OBJCOPY arch/sh/boot/zImage

Add build artifacts to 'targets' as needed.

I turned the library files to check-in files. It is simpler than
copying from arch/sh/lib/ at build-time.

Signed-off-by: Masahiro Yamada <[e-mail]>
Tested-by: John Paul Adrian Glaubitz <[e-mail]>
Signed-off-by: Rich Felker <[e-mail]>

arch/sh/boot/compressed/.gitignore

···
 # SPDX-License-Identifier: GPL-2.0-only
-ashiftrt.S
-ashldi3.c
-ashlsi3.S
-ashrsi3.S
-lshrsi3.S
 vmlinux.bin.*

arch/sh/boot/compressed/Makefile

···
 # create a compressed vmlinux image from the original vmlinux
 #
 
-targets		:= vmlinux vmlinux.bin vmlinux.bin.gz \
-		   vmlinux.bin.bz2 vmlinux.bin.lzma \
-		   vmlinux.bin.xz vmlinux.bin.lzo \
-		   head_32.o misc.o piggy.o
+OBJECTS := head_32.o misc.o cache.o piggy.o \
+           ashiftrt.o ashldi3.o ashrsi3.o ashlsi3.o lshrsi3.o
 
-OBJECTS = $(obj)/head_32.o $(obj)/misc.o $(obj)/cache.o
+# These were previously generated files. When you are building the kernel
+# with O=, make sure to remove the stale files in the output tree. Otherwise,
+# the build system wrongly compiles the stale ones.
+ifdef building_out_of_srctree
+$(shell rm -f $(addprefix $(obj)/, ashiftrt.S ashldi3.c ashrsi3.S ashlsi3.S lshrsi3.S))
+endif
+
+targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 \
+           vmlinux.bin.lzma vmlinux.bin.xz vmlinux.bin.lzo $(OBJECTS)
 
 GCOV_PROFILE := n
 
···
 LDFLAGS_vmlinux := --oformat $(ld-bfd) -Ttext $(IMAGE_OFFSET) -e startup \
 		   -T $(obj)/../../kernel/vmlinux.lds
 
-#
-# Pull in the necessary libgcc bits from the in-kernel implementation.
-#
-lib1funcs-y	:= ashiftrt.S ashldi3.c ashrsi3.S ashlsi3.S lshrsi3.S
-lib1funcs-obj   := \
-	$(addsuffix .o, $(basename $(addprefix $(obj)/, $(lib1funcs-y))))
+KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
 
-lib1funcs-dir		:= $(srctree)/arch/$(SRCARCH)/lib
-
-KBUILD_CFLAGS += -I$(lib1funcs-dir) -DDISABLE_BRANCH_PROFILING
-
-$(addprefix $(obj)/,$(lib1funcs-y)): $(obj)/%: $(lib1funcs-dir)/% FORCE
-	$(call cmd,shipped)
-
-$(obj)/vmlinux: $(OBJECTS) $(obj)/piggy.o $(lib1funcs-obj) FORCE
+$(obj)/vmlinux: $(addprefix $(obj)/, $(OBJECTS)) FORCE
 	$(call if_changed,ld)
 
 $(obj)/vmlinux.bin: vmlinux FORCE

arch/sh/boot/compressed/ashiftrt.S

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+#include "../../lib/ashiftrt.S"

arch/sh/boot/compressed/ashldi3.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+#include "../../lib/ashldi3.c"

arch/sh/boot/compressed/ashlsi3.S

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+#include "../../lib/ashlsi3.S"

arch/sh/boot/compressed/ashrsi3.S

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+#include "../../lib/ashrsi3.S"

arch/sh/boot/compressed/lshrsi3.S

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+#include "../../lib/lshrsi3.S"