python: add python_build_config property (for cross files)

Signed-off-by: Filipe Laíns <[email protected]>

docs/markdown/Machine-files.md

@@ -251,6 +251,8 @@ section.
 - `java_home` is an absolute path pointing to the root of a Java installation.
 - `bindgen_clang_arguments` an array of extra arguments to pass to clang when
   calling bindgen
+- `python_build_config` is a path to the Python build configuration file (PEP 739).
+  (*new in 1.7.0*)
 
 ### CMake variables
 

mesonbuild/envconfig.py

@@ -191,6 +191,11 @@ def get_pkg_config_libdir(self) -> T.Optional[T.List[str]]:
             assert isinstance(i, str)
         return res
 
+    def get_python_build_config(self) -> T.Optional[str]:
+        python_build_config = self.properties.get('python_build_config', None)
+        assert python_build_config is None or isinstance(python_build_config, str)
+        return python_build_config
+
     def get_cmake_defaults(self) -> bool:
         if 'cmake_defaults' not in self.properties:
             return True

mesonbuild/modules/python.py

@@ -266,7 +266,10 @@ def _dependency_method_impl(self, kwargs: TYPE_kwargs) -> Dependency:
         if dep is not None:
             return dep
 
-        build_config = self.interpreter.environment.coredata.get_option(OptionKey('python.build_config'))
+        build_config = (
+            self.interpreter.environment.properties[for_machine].get_python_build_config()
+            or self.interpreter.environment.coredata.get_option(OptionKey('python.build_config'))
+        )
 
         new_kwargs = kwargs.copy()
         new_kwargs['required'] = False
@@ -455,7 +458,10 @@ def _get_win_pythonpath(name_or_path: str) -> T.Optional[str]:
             return None
 
     def _find_installation_impl(self, state: 'ModuleState', display_name: str, name_or_path: str, required: bool) -> MaybePythonProg:
-        build_config = self.interpreter.environment.coredata.get_option(OptionKey('python.build_config'))
+        build_config = (
+            self.interpreter.environment.properties[MachineChoice.BUILD].get_python_build_config()
+            or self.interpreter.environment.coredata.get_option(OptionKey('python.build_config'))
+        )
 
         if not name_or_path:
             python = PythonExternalProgram('python3', mesonlib.python_command, build_config_path=build_config)