Make kokkos_has_string() function in Makefile.kokkos case insensitive

[akohlmey]

This simplifies the configuration and documentation when compiling Kokkos via GNU make in LAMMPS while maintaining backward compatibility.
For compiling LAMMPS with non-CMake procedure one can do:
make kokkos_cuda_mpi KOKKOS_ARCH=pascal61
or:
make kokkos_cuda_mpi KOKKOS_ARCH=Pascal61
or:
make kokkos_cuda_mpi KOKKOS_ARCH=PASCAL61
and all will have the same outcome.

This has been tested with LAMMPS on Fedora 31 Linux x86_64 only.

technical note: i looked up a way doing this without using shell commands to improve speed and portability.

[dalg24-jenkins]

Can one of the admins verify this patch?

[akohlmey]

@stanmoore1 submitted to upstream.

[stanmoore1]

I confirm this works on Power9+V100, with KOKKOS_ARCH=VOLTA70 instead of KOKKOS_ARCH=Volta70

[akohlmey]

Also tested successfully with LAMMPS on Ubuntu 18.04LTS x86_64

[codecov-commenter]

Codecov Report

Merging #3091 into develop will decrease coverage by 0.0%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           develop   #3091     +/-   ##
=========================================
- Coverage     85.7%   85.6%   -0.1%     
=========================================
  Files          122     122             
  Lines        10392   10391      -1     
=========================================
- Hits          8906    8905      -1     
  Misses        1486    1486             

Flag	Coverage Δ
#clang	76.1% <ø> (+<0.1%)	⬆️
#gcc	86.4% <ø> (-0.1%)	⬇️

Impacted Files	Coverage Δ
core/src/impl/Kokkos_HostThreadTeam.cpp	96.0% <0.0%> (-0.8%)	⬇️
core/src/OpenMP/Kokkos_OpenMP_Task.hpp	98.7% <0.0%> (-0.1%)	⬇️
core/src/impl/Kokkos_TaskQueueCommon.hpp	86.7% <0.0%> (+0.8%)	⬆️

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[crtrott]

OK to test