fix(ci): add retry for busybox download, musl cross-linker for macOS

- Add --retry 3 to busybox download (Launchpad 503 errors)
- Install musl cross-compiler on macOS for guest-agent build
- Set fail-fast: false so x86_64 isn't cancelled by aarch64 failures

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dpsoft

.github/workflows/guest-image.yml

@@ -48,7 +48,7 @@ jobs:
               DEB_URL="https://launchpad.net/ubuntu/+archive/primary/+files/busybox-static_1.36.1-6ubuntu3.1_arm64.deb"
               ;;
           esac
-          curl -fsSL "$DEB_URL" -o /tmp/busybox-static.deb
+          curl -fsSL --retry 3 --retry-delay 5 "$DEB_URL" -o /tmp/busybox-static.deb
           cd /tmp && ar x busybox-static.deb && tar xf data.tar* ./usr/bin/busybox
           chmod +x /tmp/usr/bin/busybox
 

.github/workflows/release.yml

@@ -17,6 +17,7 @@ jobs:
     name: Build Linux (${{ matrix.arch }})
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         arch: [x86_64, aarch64]
 
@@ -49,7 +50,7 @@ jobs:
               DEB_URL="https://launchpad.net/ubuntu/+archive/primary/+files/busybox-static_1.36.1-6ubuntu3.1_arm64.deb"
               ;;
           esac
-          curl -fsSL "$DEB_URL" -o /tmp/busybox-static.deb
+          curl -fsSL --retry 3 --retry-delay 5 "$DEB_URL" -o /tmp/busybox-static.deb
           cd /tmp && ar x busybox-static.deb && tar xf data.tar* ./usr/bin/busybox
           chmod +x /tmp/usr/bin/busybox
 
@@ -108,6 +109,10 @@ jobs:
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable
 
+      - name: Install musl cross-compiler
+        run: |
+          brew install messense/macos-cross-toolchains/aarch64-unknown-linux-musl
+
       - name: Build voidbox host binary
         run: |
           cargo build --release --bin voidbox