Use C locale when setting CC_VERSION_STRING and LD_VERSION_STRING.

The output reported may be locale-dependent, which results in
unreproducible builds.

  $ LANG=C ld --version | head -n 1
    GNU ld (GNU Binutils for Debian) 2.26

  $ LANG=it_CH.UTF-8 ld --version | head -n 1
    ld di GNU (GNU Binutils for Debian) 2.26

Forcing LC_ALL=C ensures the output is consistant regardless of the
build environment.

Thanks to HW42 for debugging the issue:

  https://lists.alioth.debian.org/pipermail/reproducible-builds/Week-of-Mon-20160606/005722.html

For more information about reproducible builds:

  https://reproducible-builds.org/

Signed-off-by: Vagrant Cascadian <vagrant@debian.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

Makefile

@@ -1269,8 +1269,8 @@ prepare: prepare0
 define filechk_version.h
 	(echo \#define PLAIN_VERSION \"$(UBOOTRELEASE)\"; \
 	echo \#define U_BOOT_VERSION \"U-Boot \" PLAIN_VERSION; \
-	echo \#define CC_VERSION_STRING \"$$($(CC) --version | head -n 1)\"; \
-	echo \#define LD_VERSION_STRING \"$$($(LD) --version | head -n 1)\"; )
+	echo \#define CC_VERSION_STRING \"$$(LC_ALL=C $(CC) --version | head -n 1)\"; \
+	echo \#define LD_VERSION_STRING \"$$(LC_ALL=C $(LD) --version | head -n 1)\"; )
 endef
 
 # The SOURCE_DATE_EPOCH mechanism requires a date that behaves like GNU date.