Bug#917985: OpenFOAM should not build (nor skip) dummy libraries

[Mark Olesen]

The "dummy" library files are a useful part of the OpenFOAM build 
process. They are essentially stub libraries that can act as a failsafe 
for library interfaces that are unsupported or not available on the 
system. Additionally, the dummy Pstream is an extremely useful MPI stub. 
It obviously cannot be used for parallel calculations, but does help 
solve circular linker dependencies for the gold linker, some clang 
linkers and the mingw linker.

I think that the main issue is simply messiness if these are installed 
into system locations. The merge request

https://salsa.debian.org/science-team/openfoam/-/merge_requests/4

should solve these concerns.