Set image architecture

This doesn't really matter--images will be pulled by tag and the whole
point of my images is that they are much more precise than just
architecture--but if it's going to be in the manifest, it might as well
agree with the architecture from `podman info`, which seems to use the
same names as Gentoo.

Wouldn't bother doing this if the architecture didn't cascade down to
derived images.

.gitlab-ci.yml

@@ -8,22 +8,23 @@ default:
   stage: 'build'
   tags: ['nest']
   variables:
-    ARCH: 'x86_64'
     CPU: 'haswell'
-    GENTOO_STAGE3_TAG: 'amd64'
+    GENTOO_ARCH: 'amd64'
+    QEMU_ARCH: 'x86_64'
   script: &script
     - 'mkdir debug'
     - 'buildah bud --pull --squash
+                   --arch "$GENTOO_ARCH"
                    --security-opt seccomp=unconfined
-                   --build-arg GENTOO_STAGE3_TAG="$GENTOO_STAGE3_TAG"
+                   --build-arg GENTOO_STAGE3_TAG="$GENTOO_ARCH"
                    --build-arg EMERGE_DEFAULT_OPTS="${CI_HOST_EMERGE_DEFAULT_OPTS} --usepkg"
                    --build-arg MAKEOPTS="$CI_HOST_MAKEOPTS"
                    --build-arg PROFILE="${CPU}/server"
-                   -v "/usr/bin/qemu-${ARCH}:/usr/bin/qemu-${ARCH}:ro"
+                   -v "/usr/bin/qemu-${QEMU_ARCH}:/usr/bin/qemu-${QEMU_ARCH}:ro"
                    -v "${PWD}/debug:/usr/lib/debug"
                    -v /nest:/nest
                    -t "${CI_REGISTRY_IMAGE}:${CPU}" .'
-    - 'buildah bud -t "${CI_REGISTRY_IMAGE}/debug:${CPU}" -f Containerfile.debug .'
+    - 'buildah bud --arch "$GENTOO_ARCH" -t "${CI_REGISTRY_IMAGE}/debug:${CPU}" -f Containerfile.debug .'
     - 'buildah push "${CI_REGISTRY_IMAGE}:${CPU}"'
     - 'buildah push "${CI_REGISTRY_IMAGE}/debug:${CPU}"'
 
@@ -31,7 +32,7 @@ default:
   stage: 'build'
   tags: ['nest']
   variables:
-    ARCH: 'aarch64'
     CPU: 'cortex-a72'
-    GENTOO_STAGE3_TAG: 'arm64'
+    GENTOO_ARCH: 'arm64'
+    QEMU_ARCH: 'aarch64'
   script: *script