Issue Getting Example Program to Run with Apple M3

[cmaloney111]

Describe the bug
The bug occurs when attempting to run the provided example program from the NekRS README using mpirun -np 2 nekrs --setup turbPipe.par. Initially, issues related to OpenMP linkage arise, manifesting as "no such file" errors. After attempting a fix involving setting environment variables and paths, a new error surfaces. This error indicates a problem with dlopen() and a missing symbol _adj_logical_ in the file libturbPipe.so.

To Reproduce
Steps to reproduce the behavior:

1. Follow the steps outlined in the README for building the NekRS repository.
2. Execute the example program with these steps (from the README):

   cd <directory outside of installation/source folder>
   cp -a $NEKRS_HOME/examples/turbPipePeriodic .
   mpirun -np 2 nekrs --setup turbPipe.par

3. Initially encounter OpenMP-related errors:

   dyld[90248]: Library not loaded: @rpath/libomp.dylib
     Referenced from: <BEA5CF92-0C49-30E9-A331-3C68742198F6> ~/.local/nekrs/lib/libocca.so
     Reason: tried: '~/.local/nekrs/lib/libomp.dylib' (no such file), '~/.local/nekrs/lib/libomp.dylib' (no such file), 

4. Apply the suggested fix as shown below (installing llvm and libomp using Homebrew, and setting environment variables).
5. Run the example program again, resulting in a new error:

   dlopen(~/.local/nekrs/examples/turbPipePeriodic/.cache/nek5000/libturbPipe.so, 0x0006): symbol not found in flat namespace '_adj_logical_'

Expected behavior
The example program is expected to execute successfully.

Suggested Fix For First Problem (Does Not Fix Second Problem)
To resolve the initial OpenMP linkage issue:

1. Install LLVM and libomp using Homebrew:

   brew install llvm libomp

2. Add the following environment variables to $HOME/.bash_profile for Bash:

   export LDFLAGS="-L$HOME/opt/homebrew/opt/libomp/lib $LDFLAGS"
   export CPPFLAGS="-I$HOME/opt/homebrew/opt/libomp/include $CPPFLAGS"
   export DYLD_LIBRARY_PATH="$HOME/opt/homebrew/opt/libomp/lib:$DYLD_LIBRARY_PATH"

   Alternatively, if using Zsh, place these lines in ~/.zshrc:

   export LDFLAGS="-L/opt/homebrew/opt/libomp/lib $LDFLAGS"
   export CPPFLAGS="-I/opt/homebrew/opt/libomp/include $CPPFLAGS"
   export DYLD_LIBRARY_PATH="/opt/homebrew/opt/libomp/lib:$DYLD_LIBRARY_PATH"

Finally, run either one of the following depending on what you are using:

source $HOME/.bash_profile

source ~/.zshrc

Desktop:

• OS: macOS
• Version: 15.1 (Sequoia)

[stgeke]

What Fortran compiler are you using?

[stgeke]

Regardless of the issue reported here, LLVM + ARM is currently not functional:
#485