build: consolidate NBD server build, move binary out of source tree

- Replace nbd-server-aarch64/nbd-server-x86_64 with single nbd-server
  target, auto-detecting host arch via rustc host triple. No-op on Linux
  (ifneq Linux) so macOS and future Windows both cross-compile.
- Output to target/nbd-server/ instead of source tree; build.rs
  copies into OUT_DIR for include_bytes!
- Justfile build: make nbd-server + make bin
- macOS CI simplified to just build

Assisted-by: Antigravity (Claude Opus 4.6)
Signed-off-by: Shion Tanaka <shtanaka@redhat.com>

Author: tnk4on

.github/workflows/main.yml

@@ -28,15 +28,15 @@ jobs:
         with:
           targets: aarch64-unknown-linux-gnu
 
-      - name: Install zig and cargo-zigbuild
+      - name: Install zig, cargo-zigbuild, and just
         run: |
-          brew install zig
+          brew install zig just
           cargo install cargo-zigbuild
 
-      - name: Build NBD server binary
-        run: make nbd-server-aarch64
+      - name: Build
+        run: just build
 
-      - name: Check build
+      - name: Check all targets
         run: cargo check --all-targets
 
       - name: Run unit tests

Justfile

@@ -3,9 +3,10 @@ PRIMARY_IMAGE := "quay.io/centos-bootc/centos-bootc:stream10"
 # <https://github.com/bootc-dev/bcvk/issues/153>
 ALL_BASE_IMAGES := "quay.io/fedora/fedora-bootc:43 quay.io/fedora/fedora-bootc:44 quay.io/centos-bootc/centos-bootc:stream9 quay.io/centos-bootc/centos-bootc:stream10 quay.io/almalinuxorg/almalinux-bootc:10.0"
 
-# Build the native binary
+# Build the native binary (cross-compiles NBD server on non-Linux hosts)
 build:
-   make
+    make nbd-server
+    make bin
 
 # Static checks
 validate:

Makefile

@@ -8,7 +8,6 @@ all: bin manpages
 
 .PHONY: bin
 bin:
-	cargo check --workspace
 	cargo build --release
 
 # Generate man pages from markdown sources
@@ -67,18 +66,17 @@ update-manpages:
 
 update-generated: sync-manpages manpages
 
-.PHONY: all bin install manpages update-generated makesudoinstall sync-manpages update-manpages sync-cli-options nbd-server-aarch64 nbd-server-x86_64
+.PHONY: all bin install manpages update-generated makesudoinstall sync-manpages update-manpages sync-cli-options nbd-server
 
-.PHONY: nbd-server-aarch64
-nbd-server-aarch64:
-	PATH="$(HOME)/.rustup/toolchains/stable-$(shell rustc -vV | awk '/^host:/ {print $$2}')/bin:$(HOME)/.cargo/bin:$(PATH)" \
-	  cargo zigbuild --target aarch64-unknown-linux-gnu --release -p bcvk-nbd
-	cp target/aarch64-unknown-linux-gnu/release/bcvk-nbd \
-	   crates/kit/bcvk-nbd-aarch64
+# Cross-compile NBD server for podman machine (needed on macOS/Windows, no-op on Linux)
+NBD_ARCH := $(shell rustc -vV | awk '/^host:/ {split($$2, a, "-"); print a[1]}')
+NBD_TARGET := $(NBD_ARCH)-unknown-linux-gnu
 
-.PHONY: nbd-server-x86_64
-nbd-server-x86_64:
+.PHONY: nbd-server
+nbd-server:
+ifneq ($(shell uname -s),Linux)
 	PATH="$(HOME)/.rustup/toolchains/stable-$(shell rustc -vV | awk '/^host:/ {print $$2}')/bin:$(HOME)/.cargo/bin:$(PATH)" \
-	  cargo zigbuild --target x86_64-unknown-linux-gnu --release -p bcvk-nbd
-	cp target/x86_64-unknown-linux-gnu/release/bcvk-nbd \
-	   crates/kit/bcvk-nbd-x86_64
+	  cargo zigbuild --target $(NBD_TARGET) --release -p bcvk-nbd
+	mkdir -p target/nbd-server
+	cp target/$(NBD_TARGET)/release/bcvk-nbd target/nbd-server/bcvk-nbd
+endif

crates/kit/build.rs

@@ -0,0 +1,16 @@
+//! Build script: copy cross-compiled NBD server binary into OUT_DIR for include_bytes!.
+
+fn main() {
+    // NBD server binary is needed on non-Linux hosts (macOS/Windows) where
+    // bcvk cross-compiles it for the podman machine. On Linux, the file
+    // won't exist and that's OK — nbd_macos.rs is cfg-gated.
+    let manifest_dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
+    let workspace_root = std::path::Path::new(&manifest_dir).join("../..");
+    let nbd_src = workspace_root.join("target/nbd-server/bcvk-nbd");
+    println!("cargo:rerun-if-changed={}", nbd_src.display());
+    if nbd_src.exists() {
+        let out_dir = std::env::var("OUT_DIR").unwrap();
+        let dest = std::path::Path::new(&out_dir).join("bcvk-nbd");
+        std::fs::copy(&nbd_src, &dest).expect("failed to copy bcvk-nbd to OUT_DIR");
+    }
+}

crates/kit/src/nbd_macos.rs

@@ -11,8 +11,8 @@ use tracing::info;
 use crate::utils::wait_for_readiness;
 use crate::vm_helpers;
 
-/// NBD server binary (aarch64 ELF), embedded at compile time.
-const NBD_SERVER: &[u8] = include_bytes!("../bcvk-nbd-aarch64");
+/// NBD server binary (Linux ELF for host arch), embedded at compile time.
+const NBD_SERVER: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/bcvk-nbd"));
 
 /// Deploy the NBD server binary to the podman machine.
 pub(crate) fn deploy_nbd_server(machine: &str) -> Result<()> {