Update Rust build system: use rustup with musl target for static builds

build/Dockerfile.alpine

@@ -43,7 +43,14 @@ RUN apk add --no-cache \
     grep \
     findutils \
     # JSON processing for GitHub API
-    jq
+    jq \
+    # Rustup for proper Rust musl builds
+    rustup
+
+# Setup Rust toolchain for musl builds
+RUN rustup-init -y --default-toolchain stable && \
+    . ~/.cargo/env && \
+    rustup target add x86_64-unknown-linux-musl
 
 # Create directories
 RUN mkdir -p /build/initramfs /build/kernel /build/output /build/github /build/configs/zinit /mnt/zinit