dev-libs/hsa-ext-rocr: new package

dev-libs/hsa-ext-rocr: new package

Required for the time being by dev-libs/rocm-opencl-runtime in order to
enable OpenCL image support. The relevant code will eventually be
open-sourced but so far upstream hasn't provided any timeline for it.

There is no licence file in the upstream package, that said the
libraries it contains used to be distributed as part of the AMDGPU-Pro
stack so it is a safe bet that the standalone package is covered by the
same EULA as for dev-libs/amdgpu-pro-opencl.

Package-Manager: Portage-2.3.69, Repoman-2.3.16
Signed-off-by: Marek Szuba <marecki@gentoo.org>