pylint: fix false positive for missing else branch

We cover every case as if/elif/elif. mypy can handle this fine, but
pylint doesn't do control flow or type checking and thinks in the
missing else case, the variable might not be defined.

For mypy as well, doing this instance check is unnecessary as it can be
inferred. So just micro-optimize the check and allow pylint to safely
analyze the logic.

(cherry picked from commit 29a62ff794)

mesonbuild/linkers/detect.py

@@ -45,7 +45,7 @@ def guess_win_linker(env: 'Environment', compiler: T.List[str], comp_class: T.Ty
         check_args = ['/logo', '--version']
     elif isinstance(comp_class.LINKER_PREFIX, str):
         check_args = [comp_class.LINKER_PREFIX + '/logo', comp_class.LINKER_PREFIX + '--version']
-    elif isinstance(comp_class.LINKER_PREFIX, list):
+    else: # list
         check_args = comp_class.LINKER_PREFIX + ['/logo'] + comp_class.LINKER_PREFIX + ['--version']
 
     check_args += env.coredata.get_external_link_args(for_machine, comp_class.language)