Use an arm64 pbuilder instead of cross compiling

This falls back on qemu which makes the build super slow but succesful.
Cross building Debian packages is horribly broken.

Change-Id: Ic5904ffc6eb11257fa78d5ff8de142acf1406b7b
diff --git a/packages.mk b/packages.mk
index a966914..17b974b 100644
--- a/packages.mk
+++ b/packages.mk
@@ -30,7 +30,7 @@
 		--basetgz $@ \
 		--othermirror "deb [trusted=yes] http://packages.cloud.google.com/apt mendel-day main|deb [trusted=yes] http://packages.cloud.google.com/apt mendel-bsp-$(BOARD_NAME)-day main" \
 		--distribution buster \
-		--architecture amd64 \
+		--architecture arm64 \
 		--extrapackages "crossbuild-essential-armhf crossbuild-essential-arm64 debhelper gnupg lintian" \
 		--aptcache ""
 	mkdir -p $(ROOTDIR)/cache/base-tmp