Make ARCH overrideable on the command line

Make ARCH overrideable on the command line.

Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Nigel Croxon <ncroxon@redhat.com>

Make.defaults

@@ -62,8 +62,8 @@ OBJCOPY      := $(prefix)$(CROSS_COMPILE)objcopy
 
 # Host/target identification
 OS           := $(shell uname -s)
-HOSTARCH     := $(shell $(HOSTCC) -dumpmachine | cut -f1 -d- | sed -e s,i[3456789]86,ia32, -e 's,armv7.*,arm,' )
-ARCH         := $(HOSTARCH)
+HOSTARCH     ?= $(shell $(HOSTCC) -dumpmachine | cut -f1 -d- | sed -e s,i[3456789]86,ia32, -e 's,armv7.*,arm,' )
+ARCH         ?= $(shell $(HOSTCC) -dumpmachine | cut -f1 -d- | sed -e s,i[3456789]86,ia32, -e 's,armv7.*,arm,' )
 
 # Get ARCH from the compiler if cross compiling 
 ifneq ($(CROSS_COMPILE),)