interpreter/type_checking: Add DEPEND_FILES_KW

since most of the Target classes use this, let's just go ahead and add
it here instead of moving it later

mesonbuild/interpreter/type_checking.py

@@ -10,7 +10,7 @@ from ..build import EnvironmentVariables, CustomTarget, BuildTarget
 from ..coredata import UserFeatureOption
 from ..interpreterbase import TYPE_var
 from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo
-from ..mesonlib import FileMode, MachineChoice, listify, has_path_sep
+from ..mesonlib import File, FileMode, MachineChoice, listify, has_path_sep
 
 # Helper definition for type checks that are `Optional[T]`
 NoneType: T.Type[None] = type(None)
@@ -190,3 +190,10 @@ DEPENDS_KW: KwargInfo[T.List[T.Union[BuildTarget, CustomTarget]]] = KwargInfo(
     listify=True,
     default=[],
 )
+
+DEPEND_FILES_KW: KwargInfo[T.List[T.Union[str, File]]] = KwargInfo(
+    'depend_files',
+    ContainerTypeInfo(list, (File, str)),
+    listify=True,
+    default=[],
+)