pylint: enable consider-iterating-dictionary

This didn't actually catch what it's supposed to, which is cases of:
```python
for x in dict.keys():
    y = dict[x]
```
But it did catch one unnecessary use of keys(), and one case where we
were doing something in an inefficient way. I've rewritten:
```python
if name.value in [x.value for x in self.kwargs.keys() if isinstance(x, IdNode)]:
```
as
``python
if any((isinstance(x, IdNode) and name.value == x.value) for x in self.kwargs):
```
Which avoids doing two iterations, one to build the list, and a
second to do a search for name.value in said list, which does a single
short circuiting walk, as any returns as soon as one check returns True.

.pylintrc

@@ -12,6 +12,7 @@ enable=
     bad-indentation,
     bare-except,
     compare-to-zero,
+    consider-iterating-dictionary,
     dangerous-default-value,
     deprecated-lambda,
     len-as-condition,

mesonbuild/backend/xcodebackend.py

@@ -1282,7 +1282,7 @@ def generate_single_generator_phase(self, tname, t, genlist, generator_id, objec
 
 
     def generate_pbx_sources_build_phase(self, objects_dict):
-        for name in self.source_phase.keys():
+        for name in self.source_phase:
             phase_dict = PbxDict()
             t = self.build_targets[name]
             objects_dict.add_item(t.buildphasemap[name], phase_dict, 'Sources')

mesonbuild/mparser.py

@@ -324,7 +324,7 @@ def append(self, statement: BaseNode) -> None:
             self.arguments += [statement]
 
     def set_kwarg(self, name: IdNode, value: BaseNode) -> None:
-        if name.value in [x.value for x in self.kwargs.keys() if isinstance(x, IdNode)]:
+        if any((isinstance(x, IdNode) and name.value == x.value) for x in self.kwargs):
             mlog.warning(f'Keyword argument "{name.value}" defined multiple times.', location=self)
             mlog.warning('This will be an error in future Meson releases.')
         self.kwargs[name] = value