Rule "Same architecture installation" Failed When Installing 64-bit SSDT for Visual Studio 2012

Just a quick post on an error I encountered when installing SQLServer Data Tools - Business Intelligence (SSDT-BI) for Visual Studio 2012.

The installation wouldn't even start because of a failing rule check:

Rule "Same architecture installation" failed
The CPU architecture of installing feature(s) is different than the instance specified. To continue, add features to this instance with the same architecture.

Make sure you select “New instance” on the installation dialog if you have SQL Server x64 installed. Otherwise, you probably get the error stated above!