add Ampere to known GPU architectures for Kokkos in LAMMPS easyblock

[Flamefire]

Adds CC 8.0 and 8.6

Also removes the redundant entry for lib64 (added by default, now it was duplicated) and PYTHONPATH to lib64 as that doesn't contain any python packages as far as I can tell. Querying @Darkless012 and @ocaisa for confirmation

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• SUCCESS LAMMPS-3Mar2020-foss-2020a-Python-3.8.2-kokkos.eb
• SUCCESS archspec-0.1.0-GCCcore-8.3.0-Python-3.7.4.eb
• SUCCESS gzip-1.10-GCCcore-8.3.0.eb
• SUCCESS tbb-2019_U9-GCCcore-8.3.0.eb
• SUCCESS Voro++-0.4.6-foss-2019b.eb
• SUCCESS kim-api-2.1.3-foss-2019b.eb
• SUCCESS h5py-2.10.0-foss-2019b-Python-3.7.4.eb
• SUCCESS molmod-1.4.5-foss-2019b-Python-3.7.4.eb
• SUCCESS yaff-1.6.0-foss-2019b-Python-3.7.4.eb
• SUCCESS libunistring-0.9.10-GCCcore-8.3.0.eb
• SUCCESS gc-7.6.12-GCCcore-8.3.0.eb
• SUCCESS Guile-1.8.8-GCCcore-8.3.0.eb
• SUCCESS libmatheval-1.1.11-GCCcore-8.3.0.eb
• SUCCESS PLUMED-2.5.3-foss-2019b-Python-3.7.4.eb
• SUCCESS LAMMPS-3Mar2020-foss-2019b-Python-3.7.4-kokkos.eb
• SUCCESS LAMMPS-7Aug2019-foss-2019b-Python-3.7.4-kokkos.eb

Build succeeded for 16 out of 16 (3 easyconfigs in total)
taurusi8006 - Linux centos linux 7.9.2009, x86_64, AMD EPYC 7352 24-Core Processor (zen2), Python 2.7.5
See https://gist.github.com/0fbfdafd1cefbdf7deb6ef1ba331c966 for a full test report.

[boegel]

lgtm

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS LAMMPS-3Mar2020-foss-2020a-Python-3.8.2-kokkos.eb
• SUCCESS LAMMPS-3Mar2020-intel-2020a-Python-3.8.2-kokkos.eb

Build succeeded for 2 out of 2 (2 easyconfigs in total)
node3113.skitty.os - Linux centos linux 7.9.2009, x86_64, Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz, Python 3.6.8
See https://gist.github.com/48ac5a09aff504c0995009d48754ee2f for a full test report.