Fix cross-compilation of Windows surrogate binary on Linux (#1045)

Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>

Author: ludfjig

Justfile

@@ -240,6 +240,11 @@ fmt-apply:
 clippy target=default-target: (witguest-wit)
     {{ cargo-cmd }} clippy --all-targets --all-features --profile={{ if target == "debug" { "dev" } else { target } }}  {{ target-triple-flag }} -- -D warnings
 
+# for use on a linux host-machine when cross-compiling to windows. Uses the windows-gnu which should be sufficient for most purposes
+# Note: `--all-targets` does not work because build issues from tracy-crate
+clippyw target=default-target: (witguest-wit)
+    {{ cargo-cmd }} clippy --all-features --target x86_64-pc-windows-gnu --profile={{ if target == "debug" { "dev" } else { target } }}  -- -D warnings
+
 clippy-guests target=default-target: (witguest-wit)
     cd src/tests/rust_guests/simpleguest && cargo clippy --profile={{ if target == "debug" { "dev" } else { target } }} -- -D warnings
     cd src/tests/rust_guests/witguest && cargo clippy --profile={{ if target == "debug" { "dev" } else { target } }} -- -D warnings

src/hyperlight_host/build.rs

@@ -25,10 +25,10 @@ fn main() -> Result<()> {
 
     // Windows requires the hyperlight_surrogate.exe binary to be next to the executable running
     // hyperlight. We are using rust-embed to include the binary in the hyperlight-host library
-    // and then extracting it at runtime why the surrogate process manager starts and needed pass
+    // and then extracting it at runtime when the surrogate process manager starts. We need to pass
     // the location of the binary to the rust build.
-    #[cfg(target_os = "windows")]
-    {
+    // This logic runs when targeting Windows, even if cross-compiling from Linux.
+    if std::env::var("CARGO_CFG_TARGET_OS")? == "windows" {
         println!("cargo:rerun-if-changed=src/hyperlight_surrogate/src/main.rs");
 
         // Build hyperlight_surrogate and
@@ -56,7 +56,7 @@ fn main() -> Result<()> {
         // be the same as the CARGO_TARGET_DIR for the hyperlight-host otherwise
         // the build script will hang. Using a sub directory works tho!
         // xref - https://github.com/rust-lang/cargo/issues/6412
-        let target_dir = std::path::PathBuf::from(&out_dir).join("..\\..\\hls");
+        let target_dir = std::path::PathBuf::from(&out_dir).join("../../hls");
 
         let profile = std::env::var("PROFILE")?;
         let build_profile = if profile.to_lowercase() == "debug" {
@@ -65,19 +65,29 @@ fn main() -> Result<()> {
             profile.clone()
         };
 
-        std::process::Command::new("cargo")
+        let target_triple = std::env::var("TARGET")?;
+
+        let status = std::process::Command::new("cargo")
             .env("CARGO_TARGET_DIR", &target_dir)
             .arg("build")
             .arg("--manifest-path")
             .arg(&target_manifest_path)
+            .arg("--target")
+            .arg(&target_triple)
             .arg("--profile")
             .arg(build_profile)
             .arg("--verbose")
-            .output()
-            .unwrap();
+            .status()
+            .expect("Failed to execute cargo build for surrogate");
+
+        if !status.success() {
+            panic!("Failed to build hyperlight surrogate");
+        }
 
         println!("cargo:rustc-env=PROFILE={}", profile);
-        let surrogate_binary_dir = std::path::PathBuf::from(&target_dir).join(profile);
+        let surrogate_binary_dir = std::path::PathBuf::from(&target_dir)
+            .join(&target_triple)
+            .join(profile);
 
         println!(
             "cargo:rustc-env=HYPERLIGHT_SURROGATE_DIR={}",