Prevent the use of .canonalize() on Windows

Author: mtilda

src/bootstrap/src/core/builder.rs

@@ -438,20 +438,32 @@ impl StepDescription {
             }
         }
 
-        // Resolve paths to be relative to the builder source directory.
+        // Attempt to resolve paths to be relative to the builder source directory.
         let paths: Vec<_> = paths
             .iter()
             .map(|p| {
                 // If the path does not exist, it may represent the name of a Step, such as `tidy` in `x test tidy`
                 if !p.exists() {
                     return p.clone();
                 }
-                // Get the canonical path, strip the prefix, and convert to a PathBuf.
+
+                #[cfg(windows)]
+                {
+                    if p.is_absolute() {
+                        panic!("Absolute paths are not supported on Windows");
+                    }
+
+                    // Strip current directory prefix if present
+                    return path.strip_prefix(".").unwrap_or(path).to_path_buf();
+                }
+
+                // Make the path absolute, strip the prefix, and convert to a PathBuf.
+                // FIXME: Replace `path.canonicalize()` with `std::path::absolute(path)` to support absolute paths on Windows.
                 match p.canonicalize() {
-                    Ok(p) => p.strip_prefix(&builder.src).unwrap_or(&p).to_owned(),
+                    Ok(p) => p.strip_prefix(&builder.src).unwrap_or(&p).to_path_buf(),
                     Err(e) => {
                         eprintln!("ERROR: {:?}", e);
-                        panic!("Due to the above error, failed to canonicalize path: {:?}", p);
+                        panic!("Due to the above error, failed to resolve path: {:?}", p);
                     }
                 }
             })