ci: Support for arm64 docker builds

Dockerfile

@@ -1,4 +1,4 @@
-FROM clux/muslrust:stable AS builder
+FROM messense/rust-musl-cross:x86_64-musl AS builder
 WORKDIR /usr/src
 
 # Download and compile Rust dependencies in an empty project and cache as a separate Docker layer
@@ -6,7 +6,7 @@ RUN USER=root cargo new --bin managarr-temp
 
 WORKDIR /usr/src/managarr-temp
 COPY Cargo.* .
-RUN cargo build --release --target x86_64-unknown-linux-musl
+RUN cargo build --release
 # remove src from empty project
 RUN rm -r src
 COPY src ./src
@@ -15,7 +15,7 @@ RUN rm ./target/x86_64-unknown-linux-musl/release/deps/managarr*
 
 RUN --mount=type=cache,target=/volume/target \
     --mount=type=cache,target=/root/.cargo/registry \
-    cargo build --release --target x86_64-unknown-linux-musl --bin managarr
+    cargo build --release --bin managarr
 RUN mv target/x86_64-unknown-linux-musl/release/managarr .
 
 FROM debian:stable-slim