Fix compilation of the xtask package under Windows and add to CI

.github/workflows/rust.yml

@@ -226,3 +226,25 @@ jobs:
 
     - name: Build
       run: cargo xtask test-latest-release
+
+  windows:
+    name: Check that the build works on a Windows target
+    runs-on: windows-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v2
+
+      - name: Install stable
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: stable
+
+      - name: Install latest nightly
+        uses: actions-rs/toolchain@v1
+        with:
+            profile: minimal
+            toolchain: nightly
+            components: rust-src
+
+      - name: Build
+        run: cargo xtask build

xtask/Cargo.toml

@@ -6,6 +6,7 @@ publish = false
 
 [dependencies]
 anyhow = "1.0.51"
+cfg-if = "1.0.0"
 clap = { version = "3.0.13", features = ["derive"] }
 # The latest fatfs release (0.3.5) is old, use git instead to pick up some fixes.
 fatfs = { git = "https://github.com/rafalh/rust-fatfs.git", rev = "87fc1ed5074a32b4e0344fcdde77359ef9e75432" }

xtask/src/disk.rs

@@ -1,3 +1,5 @@
+#![cfg(unix)]
+
 use anyhow::Result;
 use fatfs::{Date, DateTime, FileSystem, FormatVolumeOptions, FsOptions, StdIoWrapper, Time};
 use mbrman::{MBRPartitionEntry, CHS, MBR};

xtask/src/main.rs

@@ -8,6 +8,7 @@ mod util;
 
 use anyhow::Result;
 use cargo::{Cargo, CargoAction, Feature, Package};
+use cfg_if::cfg_if;
 use clap::Parser;
 use opt::{Action, BuildOpt, ClippyOpt, DocOpt, MiriOpt, Opt, QemuOpt};
 use std::process::Command;
@@ -102,7 +103,13 @@ fn run_vm_tests(opt: &QemuOpt) -> Result<()> {
     };
     run_cmd(cargo.command()?)?;
 
-    qemu::run_qemu(*opt.target, opt)
+    cfg_if! {
+        if #[cfg(unix)] {
+            qemu::run_qemu(*opt.target, opt)
+        } else {
+            panic!("vm tests are only supported on unix targets");
+        }
+    }
 }
 
 /// Run unit tests and doctests on the host. Most of uefi-rs is tested

xtask/src/net.rs

@@ -1,3 +1,5 @@
+#![cfg(unix)]
+
 use std::net::UdpSocket;
 
 /// Start a thread that listens on UDP port 21572 and simulates a simple echo

xtask/src/qemu.rs

@@ -1,3 +1,5 @@
+#![cfg(unix)]
+
 use crate::arch::UefiArch;
 use crate::disk::{check_mbr_test_disk, create_mbr_test_disk};
 use crate::net;