cmake: Clear INSTALL file properties between runs

Do not keep state across separate project configurations.
This is particularly important in `cmake-gui` where those
configurations can be for separate projects.

Fixes: #21580

Source/cmake.cxx

@@ -286,6 +286,8 @@ void cmake::CleanupCommandsAndMacros()
   this->CurrentSnapshot = this->State->Reset();
   this->State->RemoveUserDefinedCommands();
   this->CurrentSnapshot.SetDefaultDefinitions();
+  // FIXME: InstalledFiles probably belongs in the global generator.
+  this->InstalledFiles.clear();
 }
 
 #ifndef CMAKE_BOOTSTRAP