Bug#920585: openfoam build doesn't respect -j <n>

[Matthias Klose]

Package: src:openfoam
Version: 1812+dfsg1-1
Severity: important

looking in the build logs you see a lot of

make[5]: warning: -j3 forced in submake: resetting jobserver mode.

warnings. So the build doesn't respect the -j3 passed from the toplevel and uses
more resources than it should for the build.  Please fix the build to respect
the amount of parallelism as asked by the builders.