xen/arch/x86: make objdump output user locale agnostic

The objdump output is fed to grep, so make sure it doesn't change with
different user locales and break the grep parsing.
This problem was identified while updating xen in Debian and the fix is
needed for generating reproducible builds in varying environments.

Signed-off-by: Maximilian Engelhardt <maxi@daemonizer.de>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/arch.mk

@@ -109,7 +109,7 @@ endif
 ifeq ($(XEN_BUILD_PE),y)
 
 # Check if the linker produces fixups in PE by default
-efi-nr-fixups := $(shell $(OBJDUMP) -p $(efi-check).efi | grep '^[[:blank:]]*reloc[[:blank:]]*[0-9][[:blank:]].*DIR64$$' | wc -l)
+efi-nr-fixups := $(shell LC_ALL=C $(OBJDUMP) -p $(efi-check).efi | grep '^[[:blank:]]*reloc[[:blank:]]*[0-9][[:blank:]].*DIR64$$' | wc -l)
 
 ifeq ($(efi-nr-fixups),2)
 MKRELOC := :