mesonlib: Make a few type annotations strings

Mypy know what to do with these and isn't confused, but some versions of
python 3.5 (at least 3.5.2) can't handle these annotations. By making
them strings the python interpreter wont try to evaluate them.

Fixes #5326

mesonbuild/envconfig.py

@@ -134,7 +134,7 @@ class Properties(HasEnvVarFallback):
     def get_sys_root(self) -> typing.Optional[typing.Union[str, typing.List[str]]]:
         return self.properties.get('sys_root', None)
 
-    def __eq__(self, other: typing.Any) -> typing.Union[bool, 'NotImplemented']:
+    def __eq__(self, other: typing.Any) -> 'typing.Union[bool, NotImplemented]':
         if isinstance(other, type(self)):
             return self.properties == other.properties
         return NotImplemented
@@ -159,7 +159,7 @@ class MachineInfo:
         self.endian = endian
         self.is_64_bit = cpu_family in CPU_FAMILES_64_BIT  # type: bool
 
-    def __eq__(self, other: typing.Any) -> typing.Union[bool, 'NotImplemented']:
+    def __eq__(self, other: typing.Any) -> 'typing.Union[bool, NotImplemented]':
         if self.__class__ is not other.__class__:
             return NotImplemented
         return \
@@ -168,7 +168,7 @@ class MachineInfo:
             self.cpu == other.cpu and \
             self.endian == other.endian
 
-    def __ne__(self, other: typing.Any) -> typing.Union[bool, 'NotImplemented']:
+    def __ne__(self, other: typing.Any) -> 'typing.Union[bool, NotImplemented]':
         if self.__class__ is not other.__class__:
             return NotImplemented
         return not self.__eq__(other)

mesonbuild/mesonlib.py

@@ -920,7 +920,8 @@ def extract_as_list(dict_object, *keys, pop=False, **kwargs):
         result.append(listify(fetch(key, []), **kwargs))
     return result
 
-def typeslistify(item: typing.Union[_T, typing.List[_T]], types: typing.Union[typing.Type[_T], typing.Tuple[typing.Type[_T]]]) -> typing.List[_T]:
+def typeslistify(item: 'typing.Union[_T, typing.List[_T]]',
+                 types: 'typing.Union[typing.Type[_T], typing.Tuple[typing.Type[_T]]]') -> typing.List[_T]:
     '''
     Ensure that type(@item) is one of @types or a
     list of items all of which are of type @types