coredata: remove use of stringlistify to do a cast

This is a heavyweight and expensive function to use to verify that we
have a string list. Just cast to make mypy happy, we know what we have.

(cherry picked from commit cec99fb)

Author: dcbaker

mesonbuild/coredata.py

@@ -18,7 +18,6 @@
     MesonException, MachineChoice, PerMachine,
     PerMachineDefaultable,
     default_prefix,
-    stringlistify,
     pickle_load
 )
 
@@ -152,8 +151,8 @@ def __init__(self, builtins: options.OptionStore, for_machine: MachineChoice):
 
     def __calculate_subkey(self, type_: DependencyCacheType) -> T.Tuple[str, ...]:
         data: T.Dict[DependencyCacheType, T.List[str]] = {
-            DependencyCacheType.PKG_CONFIG: stringlistify(self.__builtins.get_value_for(self.__pkg_conf_key)),
-            DependencyCacheType.CMAKE: stringlistify(self.__builtins.get_value_for(self.__cmake_key)),
+            DependencyCacheType.PKG_CONFIG: T.cast('T.List[str]', self.__builtins.get_value_for(self.__pkg_conf_key)),
+            DependencyCacheType.CMAKE: T.cast('T.List[str]', self.__builtins.get_value_for(self.__cmake_key)),
             DependencyCacheType.OTHER: [],
         }
         assert type_ in data, 'Someone forgot to update subkey calculations for a new type'