Prevent matching bogus parent gitignores

If our project root directory is matched by an exclude pattern we
should assume the pattern is invalid as our project root is likely
in an ignored build directory of another project.

backend/src/hatchling/builders/config.py

@@ -883,6 +883,11 @@ def load_vcs_exclusion_patterns(self) -> list[str]:
                     if glob_mode:
                         patterns.append(line)
 
+        # validate project root is not excluded by vcs
+        exclude_spec = pathspec.GitIgnoreSpec.from_lines(patterns)
+        if exclude_spec.match_file(self.root):
+            return []
+
         return patterns
 
     def normalize_build_directory(self, build_directory: str) -> str: