When comiling a custom kernel using 4.14 source from git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git an error occurs executing the task do_shared_workdir:

ERROR: linux-kernel-4.14.23-r0 do_shared_workdir: Function failed: do_shared_workdir (log file is located at /home/guille/Documentos/Yocto/build-ppc64/tmp/work/powermacg5-poky-linux/linux-kernel/4.14.23-r0/temp/log.do_shared_workdir.8575)
ERROR: Logfile of failure stored in: /home/guille/Documentos/Yocto/build-ppc64/tmp/work/powermacg5-poky-linux/linux-kernel/4.14.23-r0/temp/log.do_shared_workdir.8575
Log data follows:
| DEBUG: Executing shell function do_shared_workdir
| cp: cannot stat 'arch/powerpc/lib/crtsavres.o': No such file or directory
| WARNING: /home/guille/Documentos/Yocto/build-ppc64/tmp/work/powermacg5-poky-linux/linux-kernel/4.14.23-r0/temp/run.do_shared_workdir.8575:1 exit 1 from 'cp arch/powerpc/lib/crtsavres.o $kerneldir/arch/powerpc/lib/crtsavres.o'
| ERROR: Function failed: do_shared_workdir (log file is located at /home/guille/Documentos/Yocto/build-ppc64/tmp/work/powermacg5-poky-linux/linux-kernel/4.14.23-r0/temp/log.do_shared_workdir.8575)
ERROR: Task (/home/guille/Documentos/Yocto/poky/meta-progress-bsp/recipes-kernel/linux/linux-kernel_4.14.bb:do_shared_workdir) failed with exit code '1'

The error is caused by the following code in meta/classes/kernel.bbclass

# As of Linux kernel version 3.0.1, the clean target removes
# arch/powerpc/lib/crtsavres.o which is present in
# KBUILD_LDFLAGS_MODULE, making it required to build external modules.
if [ ${ARCH} = "powerpc" ]; then
		mkdir -p $kerneldir/arch/powerpc/lib/
		cp arch/powerpc/lib/crtsavres.o $kerneldir/arch/powerpc/lib/crtsavres.o
fi

There is a change in the kernel (4.14) source that makes the previous code fail. The code can be found at arch/powerpc/lib/Makefile

obj-$(CONFIG_PPC32)	+= div64.o copy_32.o crtsavres.o

# See corresponding test in arch/powerpc/Makefile
# 64-bit linker creates .sfpr on demand for final link (vmlinux),
# so it is only needed for modules, and only for older linkers which
# do not support --save-restore-funcs
ifeq ($(call ld-ifversion, -lt, 225000000, y),y)
extra-$(CONFIG_PPC64)	+= crtsavres.o
endif

This makes behave different ppc32 and ppc64 regarding crtsavres.o

A possible fix is to repace the if condition in meta/classes/kernel.bbclass by

# As of Linux kernel version 3.0.1, the clean target removes
# arch/powerpc/lib/crtsavres.o which is present in
# KBUILD_LDFLAGS_MODULE, making it required to build external modules.
if [ ${ARCH} = "powerpc" ] && [ -e arch/powerpc/lib/crtsavres.o ]; then
		mkdir -p $kerneldir/arch/powerpc/lib/
		cp arch/powerpc/lib/crtsavres.o $kerneldir/arch/powerpc/lib/crtsavres.o
fi