build: Add macOS stub compilation support

This is the start of work on #21

Gate Linux-only modules and dependencies with #[cfg(target_os = "linux")]
so the crate compiles on macOS. For now only the `ephemeral` verb exists
as a stub that errors out, but the idea is we can fill that in.

Also replace std::process::exit(0) with Ok(()) for proper cleanup.

Assisted-by: OpenCode (Claude claude-opus-4-5@20251101)
Assisted-by: OpenCode (Claude claude-opus-4-6)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

.github/workflows/main.yml

@@ -14,6 +14,20 @@ env:
 
 
 jobs:
+  build-macos:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Check build
+        run: cargo check --all-targets
+
+      - name: Run unit tests
+        run: cargo test --lib
+
   build:
     runs-on: ubuntu-24.04
 
@@ -181,10 +195,11 @@ jobs:
   # Sentinel job for required checks - configure this job name in repository settings
   required-checks:
     if: always()
-    needs: [build, integration-tests]
+    needs: [build-macos, build, integration-tests]
     runs-on: ubuntu-latest
     steps:
       - run: exit 1
         if: >-
+          needs.build-macos.result != 'success' ||
           needs.build.result != 'success' ||
           needs.integration-tests.result != 'success'

Cargo.lock

@@ -5,10 +5,7 @@ edition = "2021"
 publish = false
 
 [dependencies]
-bcvk-qemu = { path = "../bcvk-qemu" }
 base64 = "0.22"
-# For some recent APIs, TODO switch back to published version
-cap-std-ext = { git = "https://github.com/coreos/cap-std-ext", rev = "cfdb25d51ffc697e70aa0d8d3cefe9ec2133bd0a" }
 chrono = { version = "0.4", features = ["serde"] }
 const_format = { workspace = true }
 color-eyre = { workspace = true }
@@ -17,12 +14,9 @@ clap_mangen = { version = "0.2.20", optional = true }
 data-encoding = { version = "2.9" }
 dirs = "5.0"
 fn-error-context = { version = "0.2" }
-bootc-mount = { git = "https://github.com/bootc-dev/bootc", rev = "93b22f4dbc2d54f7cca7c1df3ee59fcdec0b2cf1" }
-bootc-utils = { git = "https://github.com/bootc-dev/bootc", rev = "93b22f4dbc2d54f7cca7c1df3ee59fcdec0b2cf1" }
 indicatif = "0.17"
 notify = "6.1"
 thiserror = "1.0"
-rustix = { "version" = "1", features = ["thread", "net", "fs", "pipe", "system", "process", "mount"] }
 serde = { version = "1.0.199", features = ["derive"] }
 serde_json = "1.0.116"
 serde_yaml = "0.9"
@@ -41,9 +35,6 @@ cfg-if = { workspace = true }
 indoc = "2.0.6"
 regex = "1.10"
 itertools = "0.14.0"
-vsock = "0.5"
-nix = { version = "0.29", features = ["socket"] }
-libc = "0.2"
 camino = "1.1.12"
 comfy-table = "7.1"
 strum = { version = "0.26", features = ["derive"] }
@@ -53,6 +44,18 @@ sha2 = "0.10"
 which = "7.0"
 cpio = "0.4"
 
+# Linux-only dependencies
+[target.'cfg(target_os = "linux")'.dependencies]
+bcvk-qemu = { path = "../bcvk-qemu" }
+# For some recent APIs, TODO switch back to published version
+cap-std-ext = { git = "https://github.com/coreos/cap-std-ext", rev = "cfdb25d51ffc697e70aa0d8d3cefe9ec2133bd0a" }
+bootc-mount = { git = "https://github.com/bootc-dev/bootc", rev = "93b22f4dbc2d54f7cca7c1df3ee59fcdec0b2cf1" }
+bootc-utils = { git = "https://github.com/bootc-dev/bootc", rev = "93b22f4dbc2d54f7cca7c1df3ee59fcdec0b2cf1" }
+rustix = { version = "1", features = ["thread", "net", "fs", "pipe", "system", "process", "mount"] }
+vsock = "0.5"
+nix = { version = "0.29", features = ["socket"] }
+libc = "0.2"
+
 [dev-dependencies]
 similar-asserts = "1.5"
 

crates/kit/Cargo.toml

@@ -3,6 +3,9 @@
 //! The Linux kernel supports concatenating multiple CPIO archives,
 //! so we can simply append our files to an existing initramfs.
 
+// On non-Linux, this module is unused as it's for initramfs manipulation
+#![cfg_attr(not(target_os = "linux"), allow(dead_code))]
+
 use std::io::{self, Write};
 
 use cpio::newc::Builder as NewcBuilder;

crates/kit/src/cpio.rs

@@ -4,6 +4,9 @@
 //! operations, ensuring consistency across to-disk, libvirt-upload-disk,
 //! and other installation-related commands.
 
+// On non-Linux, this module is unused as it's for installation operations
+#![cfg_attr(not(target_os = "linux"), allow(dead_code))]
+
 use camino::Utf8PathBuf;
 use clap::Parser;
 

crates/kit/src/install_options.rs

@@ -10,6 +10,9 @@
 //!
 //! Source: https://github.com/kubevirt/common-instancetypes
 
+// On non-Linux, this module is unused as it's for VM instance types
+#![cfg_attr(not(target_os = "linux"), allow(dead_code))]
+
 /// Instance type variants with associated vCPU and memory specifications
 ///
 /// Source: https://github.com/kubevirt/common-instancetypes/blob/main/instancetypes/u/1/sizes.yaml

crates/kit/src/instancetypes.rs

@@ -1,6 +1,9 @@
 //! bcvk library - exposes internal modules for testing
 
 pub mod cpio;
-pub mod kernel;
 pub mod qemu_img;
 pub mod xml_utils;
+
+// Linux-only modules
+#[cfg(target_os = "linux")]
+pub mod kernel;