add test for preprocessing on a zig host

crates/linker/src/pe.rs

@@ -621,4 +621,77 @@ mod test {
 
         assert_eq!(new_sections, names.as_slice());
     }
+
+    #[test]
+    fn preprocess_zig_host() {
+        let host_zig = include_str!("../trivial_host.zig");
+        let app_zig = include_str!("../trivial_app.zig");
+
+        let zig = std::env::var("ROC_ZIG").unwrap_or_else(|_| "zig".into());
+
+        let dir = tempfile::tempdir().unwrap();
+        let dir = dir.path();
+
+        std::fs::write(dir.join("trivial_host.zig"), host_zig.as_bytes()).unwrap();
+        std::fs::write(dir.join("trivial_app.zig"), app_zig.as_bytes()).unwrap();
+
+        // here we would like to do
+        //
+        // let dylib_bytes = crate::generate_dylib::synthetic_dll(&["double".into(), "triple".into()]);
+        // std::fs::write(dir.join("roc-cheaty-lib.dll"), dylib_bytes).unwrap();
+        //
+        // but on windows, this is not so simple. To link a .dll into an .exe we need an additional
+        // .lib file, a so-called "import library". These are normally generated by the linker, and
+        // based on some googling there is other tooling on windows that can also generate them
+        // from a .dll. There is however very little information on what they should contain.
+        //
+        // Jakub intends to implement generating the .lib files in pure zig in the near(ish)
+        // future, so if we can wait then we can use the zig source to create our own logic for
+        // a very simple .lib file
+
+        let output = std::process::Command::new(&zig)
+            .current_dir(dir)
+            .args(&[
+                "build-lib",
+                "trivial_app.zig",
+                "-target",
+                "x86_64-windows-gnu",
+                "--strip",
+                "-OReleaseFast",
+            ])
+            .output()
+            .unwrap();
+
+        if !output.status.success() {
+            use std::io::Write;
+
+            std::io::stdout().write_all(&output.stdout).unwrap();
+            std::io::stderr().write_all(&output.stderr).unwrap();
+
+            panic!();
+        }
+
+        let output = std::process::Command::new(&zig)
+            .current_dir(dir)
+            .args(&[
+                "build-exe",
+                "trivial_host.zig",
+                "trivial_app.lib",
+                "-target",
+                "x86_64-windows-gnu",
+                "--strip",
+                "-OReleaseFast",
+            ])
+            .output()
+            .unwrap();
+
+        if !output.status.success() {
+            use std::io::Write;
+
+            std::io::stdout().write_all(&output.stdout).unwrap();
+            std::io::stderr().write_all(&output.stderr).unwrap();
+
+            panic!();
+        }
+    }
 }