Enable use of IBM XL compilers with openMP Offload support

[oseikuffuor1]

This PR applies code changes to enable building BML with IBM compilers and openMP offload support.

• Build requires setting "BML_COMPLEX =no" to avoid linker issues.
• Tested on Lassen

[jmohdyusof]

We have a lot of divergence in the code because the IBM compiler doesn't deal with firstprivate correctly. Is there a performance penalty for this version of the code, or could we improve code readability by simply using the IBM style declaration of shared arrays everywhere?

[jeanlucf22]

@oseikuffuor1 could you add the build script you use for IBM XL?

[jeanlucf22]

Some tests fail for me on Summit. I build BML like this:
module load cmake
module load cuda
module load essl
module load netlib-lapack

MY_PATH=$(pwd)

#set BLAS explicitly, otherwise cmake will pick the serial version of essl
export BLAS_LIBRARIES=${BLAS_LIBRARIES:="$OLCF_ESSL_ROOT/lib64/libesslsmp.so"}
#since essl does not contain all the lapack functions needed, we still need lapack
export LAPACK_LIBRARIES=${LAPACK_LIBRARIES:="$OLCF_NETLIB_LAPACK_ROOT/lib64/liblapack.so"}

export CC=${CC:=mpicc}
export FC=${FC:=mpif90}
export CXX=${CXX:=mpicxx}

export BML_OPENMP=${BML_OPENMP:=yes}
export BML_OMP_OFFLOAD=${BML_OMP_OFFLOAD:=yes}
export BML_CUSPARSE=${BML_CUSPARSE:=yes}
export BML_COMPLEX=${BML_COMPLEX:=no}
export INSTALL_DIR=${INSTALL_DIR:="${MY_PATH}/install"}
export BML_TESTING=${BML_TESTING:=yes}
export CMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE:=Release}

[jeanlucf22]

Actually, with that build script, there was no OpenMP offload. After fixing it, it passes the tests