feat: add ARM64 musl binary support for complete Alpine coverage

- Download radar-agent-linux-arm64-musl binary from radar repo
- Update Alpine Dockerfile to use ARM64 musl binary instead of glibc
- Remove libgcc dependency (no longer needed with musl binary)
- Add radar-agent-linux-arm64-musl to release artifacts
- Update release notes with ARM64 musl download instructions

This completes the multi-platform support matrix:
- Debian images: AMD64 glibc + ARM64 glibc
- Alpine images: AMD64 musl + ARM64 musl

All platforms now use the correct libc for their base image.

Author: joshrotenberg

.github/workflows/release.yml

@@ -34,6 +34,8 @@ jobs:
           cp ./binaries/radar-agent-linux/radar-agent-linux ./radar-agent-linux
           cp ./binaries/radar-agent-linux-musl/radar-agent-linux-musl ./radar-agent-linux-musl
           cp ./binaries/radar-agent-linux-arm64/radar-agent-linux-arm64 ./radar-agent-linux-arm64
+            radar-agent-linux-arm64-musl
+          cp ./binaries/radar-agent-linux-arm64-musl/radar-agent-linux-arm64-musl ./radar-agent-linux-arm64-musl
           cp ./binaries/radar-agent-darwin/radar-agent-darwin ./radar-agent-darwin
 
           # Make binaries executable
@@ -53,6 +55,7 @@ jobs:
             radar-agent-linux
             radar-agent-linux-musl
             radar-agent-linux-arm64
+            radar-agent-linux-arm64-musl
             radar-agent-darwin
           retention-days: 1
 
@@ -172,6 +175,7 @@ jobs:
             radar-agent-linux
             radar-agent-linux-musl
             radar-agent-linux-arm64
+            radar-agent-linux-arm64-musl
             radar-agent-darwin
           make_latest: true
           body: |
@@ -189,7 +193,12 @@ jobs:
             curl -L "https://github.com/redis-field-engineering/radar-agent/releases/download/${{ steps.tag.outputs.tag_name }}/radar-agent-linux-musl" -o radar-agent
             ```
 
-            **Linux ARM64:**
+            **Linux ARM64 (glibc):**
+
+            **Linux ARM64 (musl - for Alpine):**
+            ```bash
+            curl -L "https://github.com/redis-field-engineering/radar-agent/releases/download/${{ steps.tag.outputs.tag_name }}/radar-agent-linux-arm64-musl" -o radar-agent
+            ```
             ```bash
             curl -L "https://github.com/redis-field-engineering/radar-agent/releases/download/${{ steps.tag.outputs.tag_name }}/radar-agent-linux-arm64" -o radar-agent
             ```

docker/Dockerfile.alpine.multiplatform

@@ -10,8 +10,7 @@ LABEL org.opencontainers.image.source="https://github.com/redis-field-engineerin
 # Install required packages and create user
 RUN apk add --no-cache \
     ca-certificates \
-    curl \
-    libgcc && \
+    curl && \
     adduser -D -g "" appuser
 
 # Create necessary directories
@@ -22,13 +21,12 @@ RUN mkdir -p /certs /etc/agent /home/appuser/bin && \
 COPY --chown=appuser:appuser radar-agent-config-sample.yml /etc/agent/config.yaml
 
 # Copy the correct binary based on architecture
-# For Alpine, we use musl binaries
-# Note: Currently we only have musl for amd64, so arm64 will use glibc binary
+# For Alpine, we use musl binaries for both AMD64 and ARM64
 COPY radar-agent-linux* /tmp/
 RUN if [ "$TARGETARCH" = "amd64" ]; then \
-      cp /tmp/radar-agent-linux-musl /usr/local/bin/radar-agent || cp /tmp/radar-agent-linux /usr/local/bin/radar-agent; \
+      cp /tmp/radar-agent-linux-musl /usr/local/bin/radar-agent; \
     elif [ "$TARGETARCH" = "arm64" ]; then \
-      cp /tmp/radar-agent-linux-arm64 /usr/local/bin/radar-agent; \
+      cp /tmp/radar-agent-linux-arm64-musl /usr/local/bin/radar-agent; \
     fi && \
     chmod +x /usr/local/bin/radar-agent && \
     rm -rf /tmp/radar-agent-*