Build failures when link MFMG/no CUDA against DealII/CUDA

[aprokop]

<snip>
/usr/local/cuda-8.0/lib64/libcusolver.so: undefined reference to `GOMP_parallel_start'
/usr/local/cuda-8.0/lib64/libcusolver.so: undefined reference to `GOMP_critical_end'
<snip>

-fopenmp flag is present in the link, and is after cusolver. DealII was installed through spack. This does not happen when DealII is installed independently.

Enabling CUDA in MFMG leads to successful linking.

[Rombur]

Yeah there is a bug with the current development version of dealii where -fopenmp is not passed correctly when cusolver is used https://cdash.kyomu.43-1.org/testDetails.php?test=8527129&build=1390 I am hoping to fix it this week end.

[masterleinad]

I am seeing similar issues if deal.II is built with CUDA support, but mfmg isn't.