arglist: post is only appended to, make it a list

self.post is only ever appended to on the right hand.  However,
it is then reversed twice in flush_pre_post(), by using "for a in
reversed.post()" and appendleft() within the loop.  It would be tempting
to use appendleft() in __iadd__ to avoid the call to reversed(), but that
is not a good idea because the loop of flush_pre_post() is part of a slow
path.  It's rather more important to use a fast extend-with-list-argument
in the fast path where needs_override_check if False.

For clarity, and to remove the temptation, make "post" a list instead
of a deque.

Signed-off-by: Paolo Bonzini <[email protected]>

mesonbuild/arglist.py

@@ -106,7 +106,7 @@ def __init__(self, compiler: T.Union['Compiler', 'StaticLinker'],
         self._container: T.List[str] = list(iterable) if iterable is not None else []
 
         self.pre: T.Deque[str] = collections.deque()
-        self.post: T.Deque[str] = collections.deque()
+        self.post: T.List[str] = []
         self.needs_override_check: bool = False
 
     # Flush the saved pre and post list into the _container list