CMake: pro2cmake.py: Fix merging of scopes

Set new keys in the parent scope instead of just appending to existing
scopes.

Change-Id: I901c3f418429d8aed56acb39b1dbe566c5468920
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

util/cmake/pro2cmake.py

@@ -213,7 +213,10 @@ class Scope:
             self._add_child(c)
 
         for key in other._operations.keys():
-            self._operations[key] = other._operations[key]
+            if key in self._operations:
+                self._operations[key] += other._operations[key]
+            else:
+                self._operations[key] = other._operations[key]
 
     def basedir(self) -> str:
         return self._basedir