tools/mkimage: backport SOURCE_DATE_EPOCH for reproducible builds

This pulls in Paul Kocialkowski's SOURCE_DATE_EPOCH support patch for u-boot,
which landed upstream circa July 2015. Note that this "host" u-boot repo is
only used to compile the 'mkimage' utility, and isn't used to actually compile
a bootloader for any target.

This patch could be removed if/when the host u-boot package is updated to a
contemporary version (but there doesn't seem to be any motivation/need to do
so).

Signed-off-by: bryan newbold <bnewbold@robocracy.org>
Signed-off-by: Felix Fietkau <nbd@openwrt.org> [fix portability error, refresh patches]

SVN-Revision: 48542

tools/mkimage/patches/200-gcc5_compat.patch

@@ -17,9 +17,6 @@ Signed-off-by: Hans de Goede <hdegoede@redhat.com>
  1 file changed, 65 insertions(+)
  create mode 100644 include/linux/compiler-gcc5.h
 
-diff --git a/include/linux/compiler-gcc5.h b/include/linux/compiler-gcc5.h
-new file mode 100644
-index 0000000..c8c5659
 --- /dev/null
 +++ b/include/linux/compiler-gcc5.h
 @@ -0,0 +1,65 @@
@@ -88,6 +85,3 @@ index 0000000..c8c5659
 +#define __HAVE_BUILTIN_BSWAP64__
 +#define __HAVE_BUILTIN_BSWAP16__
 +#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
--- 
-1.7.10.4
-