kbuild/arch/xtensa: Define LINKER_SCRIPT for the linker script

Define the LINKER_SCRIPT when building the linker script as being done
in other architectures. This is required, because upcoming Makefile changes
would otherwise break things.
Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-xtensa@linux-xtensa.org
Link: http://lkml.kernel.org/r/20181003213100.189959-2-namit@vmware.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/xtensa/kernel/Makefile

@@ -35,8 +35,8 @@ sed-y = -e ':a; s/\*(\([^)]*\)\.text\.unlikely/*(\1.literal.unlikely .{text}.unl
 	-e 's/\.{text}/.text/g'
 
 quiet_cmd__cpp_lds_S = LDS     $@
-cmd__cpp_lds_S = $(CPP) $(cpp_flags) -P -C -Uxtensa -D__ASSEMBLY__ $<    \
-                 | sed $(sed-y) >$@
+cmd__cpp_lds_S = $(CPP) $(cpp_flags) -P -C -Uxtensa -D__ASSEMBLY__ \
+		 -DLINKER_SCRIPT $< | sed $(sed-y) >$@
 
 $(obj)/vmlinux.lds: $(src)/vmlinux.lds.S FORCE
 	$(call if_changed_dep,_cpp_lds_S)