sysdetect: building with MPI support requires user code to build with MPI

[Daniel Barry]

The sysdetect component uses MPI (if available) so that each thread can see available GPUs (provided by ‘nvidia_gpu.c’). However, this in turn requires user applications to build with MPI. Otherwise, the following errors appear:

~/myapps/papi/lib/libpapi.so: undefined reference to `ompi_mpi_info_null'
~/myapps/papi/lib/libpapi.so: undefined reference to `ompi_mpi_comm_world'
~/myapps/papi/lib/libpapi.so: undefined reference to `ompi_mpi_win_null'

Also, when MPI is not available, the following error appears during the build process:

free -I../../.. -o query_device_simple_f query_device_simple_f.F ../../../libpapi.a -ldl
free: invalid option -- 'I'

‌

[Daniel Barry]

This issue has been resolved by commit 482e8c5.