find_package should now be the only way to import ROCclr. Also update
the build example comment.
The build scripts used 2 custom variables to manually specify the
build and source directories for where to find VDI. Once renamed to
ROCclr, these conflicted with the variables automatically set by
find_package(ROCclr). These hacks tried to satisfy this intermediate
step to try satisfying commit ordering problems to get through PSDB.
The INSTALL.md documentation should also be updated, but it's
completely missing any mention of ROCclr now, and still gives
directions for hcc.
Change-Id: I6fc94b6cb36241a9d4f22d24e49523367f803461
Matt Arsenault
a98920d9a3