ARM: 9038/1: Link with '-z norelro'

When linking a multi_v7_defconfig + CONFIG_KASAN=y kernel with
LD=ld.lld, the following error occurs:

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- LLVM=1 zImage
ld.lld: error: section: .exit.data is not contiguous with other relro sections

LLD defaults to '-z relro', which is unneeded for the kernel because
program headers are not used nor is there any position independent code
generation or linking for ARM. Add '-z norelro' to LDFLAGS_vmlinux to
avoid this error.

Link: https://github.com/ClangBuiltLinux/linux/issues/1189Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/Makefile

@@ -10,7 +10,7 @@
 #
 # Copyright (C) 1995-2001 by Russell King
 
-LDFLAGS_vmlinux	:= --no-undefined -X --pic-veneer
+LDFLAGS_vmlinux	:= --no-undefined -X --pic-veneer -z norelro
 ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
 LDFLAGS_vmlinux	+= --be8
 KBUILD_LDFLAGS_MODULE	+= --be8