A recent change to the rendering library has a source code in the
internal subdirectory references from the rendering directory. This
makes sense as we want all the components (whether externally visible or
not) to be in the same library. However this broke the SourceInBuild
tests as the source code was technically not referenced from the
CMakeLists.txt in the same directory.

Anticipating that this could be a common occurance, I modified the test
to also check the CMakeLists.txt in the parent directory.