qmake: Avoid comparison of values with different enumeration types

A switch statement using enumeration type midlErrorCheckOption as
condition had an enumeration value from type midlStructMemberAlignOption
as a case label. This had only coincidentally the intended effect, since
the intended value (midlErrorCheckOption::midlEnableCustom) and the
actually used one
(midlStructMemberAlignOption::midlStructMemberAlignOption) have both
the value 0.

Change-Id: I73b337f23e733a1a6fb80517e29365e01838238a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

qmake/generators/win32/msbuild_objectmodel.cpp

@@ -1201,7 +1201,7 @@ static inline QString toString(midlCharOption option)
 static inline QString toString(midlErrorCheckOption option)
 {
     switch (option) {
-    case midlAlignNotSet:
+    case midlEnableCustom:
         break;
     case midlDisableAll:
         return "None";