Revert "Making sure that the TestingExternal projects can be build with install tree"

This reverts commit 341ea97e6cfb2c64c24aa3fc1c7f98aa73291af9.

Change-Id: I4be82c6dab4892e8ec0b998377e74531cc7a6536
Merge topic 'revert-include-source-file-from-install-tree' into master

bf3c1599 Revert "Making sure that the TestingExternal projects can be build with install tree"