If the user is holding the SHIFT key while placing a new building for construction, the building remains selected for the user to place a new one again. Like in Age of Empires or similar games.

End result:
  1. Open the build menu.
  2. Select the building you want to build.
  3. Locate the location of the new building and SHIFT+CLICK.
  4. Now SHIFT+CLICK in a new location to place a second one.
  5. Now SHIFT+CLICK for a third instance, etc.

No need to keep on selecting from the building menu over and over and over ....