BuildInfo: Fix operator == to work better with subtypes

Different buildconfigurationfactories will always return different
BuildInfo, as the factories will turn the information into a different
set of objects (even if the information those objects are created from
are identical).

Each factory will always produce the same (sub-)type of BuildInfo, as
they need that information to proceed. So using the factory-address
as a kind of type-identifier is save.

Change-Id: Ia30355c26e045d453c0c2b75da893a4bac38b048
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cmakeprojectmanager/cmakeconfigitem.cpp

@@ -177,4 +177,10 @@ QString CMakeConfigItem::toString() const
     return QString::fromUtf8(key) + QLatin1Char(':') + typeStr + QLatin1Char('=') + QString::fromUtf8(value);
 }
 
+bool CMakeConfigItem::operator==(const CMakeConfigItem &o) const
+{
+    // type, isAdvanced and documentation do not matter for a match!
+    return o.key == key && o.value == value;
+}
+
 } // namespace CMakeProjectManager