Since Intel's default openmp implementation is available in the same src
tarball, we can just include it in the package. This means that `mkl` now "just
works" without any environment variables, fragile setup-hooks, or forced
propagation.
Since the openmp implementation is only needed at runtime (and for test cases),
users can substitute a different one if they prefer by exporting it with
`LD_PRELOAD`, which is how Intel recommends handling this. If they do not do so,
`libiomp.so` lives next to `libmkl_rt.so` and thus will be in the RPATH as a
sane default.
Since this still comes from the same src tarball, we can ship it without losing
the fixed-output derivation; likewise, since Hydra is not building or caching
these, shipping these proprietary packages costs no bandwidth for the nix
community.
This packags the Intel Math Kernel library on x86-64 platforms, which is a
dependency for many data science and machine learning packages.
Upstream, Intel provides proprietary binary RPMs with a permissive
redistribution license. These have been repackaged in both Debian and Anaconda,
so we are not the first distribution to redistribute.
