fix(hole-punch): Add support for arm64 architecture (#4687)

hole-punching-tests/Dockerfile

@@ -1,21 +1,19 @@
 # syntax=docker/dockerfile:1.5-labs
 FROM rust:1.73.0 as builder
 
-RUN rustup target add x86_64-unknown-linux-musl
-RUN --mount=type=cache,target=/var/cache/apt apt-get update && apt-get install -y musl-dev musl-tools
-
 # Run with access to the target cache to speed up builds
 WORKDIR /workspace
 ADD . .
+
+# Build the relay as a statically-linked binary. Unfortunately, we must specify the `--target` explicitly. See https://msfjarvis.dev/posts/building-static-rust-binaries-for-linux/.
 RUN --mount=type=cache,target=./target \
     --mount=type=cache,target=/usr/local/cargo/registry \
-    cargo build --release --package hole-punching-tests --target x86_64-unknown-linux-musl
+    RUSTFLAGS='-C target-feature=+crt-static' cargo build --release --package hole-punching-tests --target $(rustc -vV | grep host | awk '{print $2}')
 
 RUN --mount=type=cache,target=./target \
-    mv ./target/x86_64-unknown-linux-musl/release/hole-punching-tests /usr/local/bin/hole-punching-tests
+    mv ./target/$(rustc -vV | grep host | awk '{print $2}')/release/hole-punching-tests /usr/local/bin/hole-punching-tests
 
 FROM alpine:3
 COPY --from=builder /usr/local/bin/hole-punching-tests /usr/bin/hole-punch-client
 RUN --mount=type=cache,target=/var/cache/apk apk add bind-tools jq curl tcpdump iproute2-tc
-
 ENV RUST_BACKTRACE=1