fix(ci): resolve a bare drive WORKDIR to the drive root (#3258)

tools/ci/src/desktop.rs

@@ -495,10 +495,18 @@ fn workspace_dir() -> PathBuf {
 
 fn workdir() -> PathBuf {
     env::var("WORKDIR")
-        .map(PathBuf::from)
+        .map(|value| workdir_path(&value))
         .unwrap_or_else(|_| workspace_dir())
 }
 
+fn workdir_path(value: &str) -> PathBuf {
+    let bytes = value.as_bytes();
+    if bytes.len() == 2 && bytes[0].is_ascii_alphabetic() && bytes[1] == b':' {
+        return PathBuf::from(format!("{value}\\"));
+    }
+    PathBuf::from(value)
+}
+
 fn desktop_dist_dir() -> PathBuf {
     workdir().join("fluxer_desktop").join("dist-electron")
 }
@@ -5584,6 +5592,17 @@ mod tests {
             .unwrap()
     }
 
+    #[test]
+    fn bare_drive_workdir_resolves_to_the_drive_root() {
+        assert_eq!(workdir_path("W:"), PathBuf::from("W:\\"));
+        assert_eq!(workdir_path("w:"), PathBuf::from("w:\\"));
+        assert_eq!(workdir_path("W:\\src"), PathBuf::from("W:\\src"));
+        assert_eq!(
+            workdir_path("/home/runner/work"),
+            PathBuf::from("/home/runner/work")
+        );
+    }
+
     fn matrix_args() -> BuildDesktopArgs {
         BuildDesktopArgs {
             step: DesktopStep::SetMatrix,