docker: Add Instruction Set Architectures to build matrix.

ci: Publish multi-arch images for both branch and tag refs.

Signed-off-by: Jason Volk <jason@zemos.net>

docker/Dockerfile.rust

@@ -16,7 +16,7 @@ RUN <<EOF
     var="${rustup_version}/${rust_target}"
     url="https://static.rust-lang.org/rustup/archive/$var/rustup-init"
     curl -S -O -s "$url"
-    chmod o+x rustup-init
+    chmod a+rx rustup-init
 EOF
 
 FROM input AS rust
@@ -54,7 +54,7 @@ RUN \
         --no-update-default-toolchain \
         --no-modify-path
 
-    chmod -R go+rw $CARGO_HOME $RUSTUP_HOME
+    chmod -R a+rw $CARGO_HOME $RUSTUP_HOME
     rm rustup-init
 
     rustup component add \