remove useless variables that are no longer or were never used

mesonbuild/backend/vs2010backend.py

@@ -1194,7 +1194,6 @@ class Vs2010Backend(backends.Backend):
                     l = t.extract_all_objects(False)
 
                     # Unforunately, we can't use self.object_filename_from_source()
-                    gensrclist: T.List[File] = []
                     for gen in l.genlist:
                         for src in gen.get_outputs():
                             if self.environment.is_source(src) and not self.environment.is_header(src):

mesonbuild/backend/xcodebackend.py

@@ -623,7 +623,6 @@ class XCodeBackend(backends.Backend):
                     fullpath = os.path.join(self.environment.get_build_dir(), s)
                 else:
                     fullpath = os.path.join(self.environment.get_source_dir(), s)
-                compiler_args = ''
                 sdict.add_item('isa', 'PBXBuildFile')
                 sdict.add_item('fileRef', fileref, fullpath)
                 objects_dict.add_item(idval, sdict)

mesonbuild/coredata.py

@@ -737,7 +737,7 @@ class CoreData:
                 self.options[key] = value
                 try:
                     value.set_value(oldval.value)
-                except MesonException as e:
+                except MesonException:
                     mlog.warning(f'Old value(s) of {key} are no longer valid, resetting to default ({value.value}).')
 
     def is_cross_build(self, when_building_for: MachineChoice = MachineChoice.HOST) -> bool: