fix: honor the current working directory when importing pdm_build.py

Close #245

Signed-off-by: Frost Ming <me@frostming.com>

src/pdm/backend/base.py

@@ -134,7 +134,10 @@ def get_hooks(self) -> Iterable[BuildHookInterface]:
         local_hook = self.config.build_config.custom_hook
         if local_hook is not None:
             yield cast(
-                BuildHookInterface, import_module_at_path(self.location / local_hook)
+                BuildHookInterface,
+                import_module_at_path(
+                    self.location / local_hook, context=self.location
+                ),
             )
 
     def call_hook(

src/pdm/backend/utils.py

@@ -152,14 +152,18 @@ def replace_func(match: Match[str]) -> str:
 
 
 def import_module_at_path(
-    src_path: str | Path, module_name: str = "_local"
+    src_path: str | Path, module_name: str = "_local", context: Path | None = None
 ) -> types.ModuleType:
     """Import a module from a given path."""
     spec = importlib.util.spec_from_file_location(module_name, src_path)
     if spec is None:
         raise ValueError(f"Could not import module {module_name} from {src_path}")
+    if context is not None:
+        sys.path.insert(0, str(context.absolute()))
     module = importlib.util.module_from_spec(spec)
     spec.loader.exec_module(module)  # type: ignore
+    if context is not None:
+        sys.path.pop(0)
     return module