s390/kpatch-build: add -fPIC flag with -mno-pic-data-is-text-relative

-mno-pic-data-is-text-relative compiler flag expects -fPIC/-fPIE flag
along with it.  Since kernel commit 778666df60f0 ("s390: compile
relocatable kernel without -fPIE"), the -fPIC/-fPIE flag is missing when
creating kpatch module and this can lead to the following error:

cc1: error: ‘-mno-pic-data-is-text-relative’ cannot be used without
‘-fpic’/‘-fPIC’.

Previously kpatch-build didnt show up this issue, as the previous kernel
was built with -fPIE.

Fix kpatch-build by including -fPIC flag in ARCH_KCFLAGS for s390
platform. This ensures compatibility of kpatch-build with the latest
kernel.

Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>

kpatch-build/kpatch-build

@@ -1237,6 +1237,7 @@ fi
 
 if [[ "$ARCH" = "s390x" ]]; then
 	ARCH_KCFLAGS="-mno-pic-data-is-text-relative -fno-section-anchors"
+	kernel_version_gte 6.9.0 && ARCH_KCFLAGS+=" -fPIC"
 fi
 
 export KCFLAGS="-I$DATADIR/patch -ffunction-sections -fdata-sections \