nvc++: add -Mnofma to compiler flags

[BenWibking]

Describe the bug
We don't currently disable FMA instructions when compiling with nvc++, since it uses compiler flags that differ from gcc and clang.

We can fix this:

• For host code: add -Mnofma (https://forums.developer.nvidia.com/t/nvc-disable-fma-generation-in-host-code/308179).
• For GPU code: add -gpu=nofma (https://docs.nvidia.com/hpc-sdk/compilers/hpc-compilers-user-guide/index.html#gpu).

To Reproduce
Steps to reproduce the behavior:

1. Compile any problem with -DCMAKE_CXX_COMPILER=nvc++.
2. See error.

Additional context
https://forums.developer.nvidia.com/t/nvc-disable-fma-generation-in-host-code/308179