Nirbheek Chauhan authored Jul 06, 2020 and GStreamer Marge Bot committed Jul 09, 2020

We've been doing this since the beginning to ensure correct paths
inside various files such as .pc and .la, but we this is not needed
anymore for two reasons:

1. We ship pkg-config with --define-prefix enabled
2. MSI supports installing into any location

So, always use dirs inside the build/ directory.

Part-of: <!537>