kmod: pass CFLAGS_MODULE to module build

The kmod/patch/Makefile defines KBUILD_CFLAGS_MODULE, but it seems that
kbuild doesn't honor it as environment variable.  This is noticed when
attempting to use the kpatch-build --non-replace option: the flag is
added to KBUILD_CFLAGS_MODULE, yet the kernel module build ignores it.

At the same time, the kernel docs suggest passing CFLAGS_MODULE [1], not
KBUILD_CFLAGS_MODULE, from the commandline.  Setup KPATCH_MAKE to pass
these options through that variable.

[1] https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt

Fixes: c14e6e9 ("kpatch-build: Add PPC64le livepatch support")
Fixes: 17dcebf ("kpatch-build: enable klp with replace option by default")
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

Author: joe-lawrence

kmod/patch/Makefile

@@ -1,13 +1,13 @@
 KPATCH_BUILD ?= /lib/modules/$(shell uname -r)/build
-KPATCH_MAKE = $(MAKE) -C $(KPATCH_BUILD) M=$(PWD)
+KPATCH_MAKE = $(MAKE) -C $(KPATCH_BUILD) M=$(PWD) CFLAGS_MODULE='$(CFLAGS_MODULE)'
 LDFLAGS += $(KPATCH_LDFLAGS)
 
 # ppc64le kernel modules are expected to compile with the
 # -mcmodel=large flag.  This enables 64-bit relocations
 # instead of a 32-bit offset from the TOC pointer.
 PROCESSOR = $(shell uname -m)
 ifeq ($(PROCESSOR), ppc64le)
-KBUILD_CFLAGS_MODULE += -mcmodel=large
+CFLAGS_MODULE += -mcmodel=large
 endif
 
 obj-m += $(KPATCH_NAME).o

kpatch-build/kpatch-build

@@ -839,7 +839,7 @@ if grep -q "CONFIG_LIVEPATCH=y" "$CONFIGFILE" && (kernel_is_rhel || kernel_versi
 	if [[  "$KLP_REPLACE" -eq 1 ]] ; then
 		support_klp_replace || die "The kernel doesn't support klp replace"
 	else
-		export KBUILD_CFLAGS_MODULE="$KBUILD_CFLAGS_MODULE -DKLP_REPLACE_ENABLE=false"
+		export CFLAGS_MODULE="$CFLAGS_MODULE -DKLP_REPLACE_ENABLE=false"
 	fi
 else
 	# No support for livepatch in the kernel. Kpatch core module is needed.