Icons visible through terrain when building menu is open

Issue description

When the building menu is open, certain icons such as building inputs/outputs, are visible through the terrain.

I'd have expected these to be obscured by e.g. mountain ranges.

Reproduction steps

1. Start a new game on a map with large height differences.
2. Place a building (e.g. coal maker) on high ground, but close to a mountain.
3. Look at the building from the other side of the mountain.
4. Open the build menu.
5. Observe the icons rendered through the terrain.

Game version and build number

v0.6.0

Operating system

Windows

Attachments

Notice all the icons rendered through the terrain in the center.

This isn't new BTW.