Patch merged into coreboot/master: rules.h: Add ENV_ macros to detect current architecture

the following patch was just integrated into master:
commit d3634c108d63d07ce004a66e3abb05e8da57d65b
Author: Julius Werner 
Date:   Fri Nov 13 13:28:41 2015 -0800

rules.h: Add ENV_ macros to detect current architecture

This patch expands the existing ENV_<stage> macros in <rules.h> with a
    set of ENV_<arch> macros which can be used to detect which architecture
    the current compilation unit is built for. These are more consistent
    than compiler-defined macros (like '#ifdef __arm__') and will make it
    easier to write small, architecture-dependent differences in common code
    (where we currently often use IS_ENABLED(CONFIG_ARCH_...), which is
    technically incorrect in a world where every stage can run on a
    different architecture, and merely kinda happened to work out for now).

Also remove a vestigal <arch/rules.h> from ARM64 which was no longer
    used, and genericise ARM subarchitecture Makefiles a little to make
    things like __COREBOOT_ARM_ARCH__ available from all file types
    (including .ld).

BUG=None
    TEST=Compiled Falco, Blaze, Jerry and Smaug.

Change-Id: Id51aeb290b5c215c653e42a51919d0838e28621f
    Signed-off-by: Julius Werner 
    Reviewed-on: http://review.coreboot.org/12433
    Tested-by: build bot (Jenkins)
    Reviewed-by: Aaron Durbin 
    Reviewed-by: Kyösti Mälkki 
    Tested-by: Raptor Engineering Automated Test Stand

See http://review.coreboot.org/12433 for details.

-gerrit