kernel config project: s/x86/x86_64

Let's use the kernel machine architecture for this value.

Also remove a broken check. The "arch" binary on OSX outputs different
stuff than on linux. Since we don't need this check anyway  (the variable
is mostly to demonstrate how cross platform stuff would work, not to
actually do it yet), let's just remove the check.

Signed-off-by: Tycho Andersen <tycho@docker.com>

projects/kernel-config/Makefile

@@ -12,7 +12,7 @@
 HASH?=$(shell git ls-tree HEAD -- ../$(notdir $(CURDIR)) | awk '{print $$3}')
 # Name on Hub
 IMAGE:=kernel
-ARCH?=$(shell if [ "$$(arch)" = "x86_64" ]]; then echo x86; else $$(arch); fi)
+ARCH?=x86_64
 
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