tests: Remove hard-coded references to x86_64

Distributions run these tests on other architectures, but hard-coding
x86_64 to look for in output dooms that to failure.

Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit ba381ae)
(cherry picked from commit 4089b69)

tests/test-oci.sh

@@ -51,7 +51,7 @@ image=oci/image/blobs/sha256/$DIGEST
 assert_has_file $image
 assert_file_has_content $image "org\.freedesktop\.appstream\.appdata.*<summary>Print a greeting</summary>"
 assert_file_has_content $image "org\.freedesktop\.appstream\.icon-64"
-assert_file_has_content $image org.flatpak.ref.*app/org.test.Hello/x86_64/master
+assert_file_has_content $image org.flatpak.ref.*app/"org.test.Hello/$ARCH/master"
 
 ok "export oci"