unload errors for fieldfunctions library

The recent changes to phase-system turbulence libraries and subsequent change to the field function link options (commit 11965904) appear to provoke an unload error. Seen for clang (10.0), but not for gcc (7.5.0).

If I do a full or partial revert of that commit, the error shifts to being not able to load the library (double entry for "laminar" as @Pawan reported).

Here is what the error currently looks like:

tutorials/heatTransfer/chtMultiRegionFoam/externalCoupledHeater/

$ foamListRegions
bottomWater
topAir
heater
leftSolid
rightSolid
--> FOAM Warning : 
    From void Foam::dlLibraryTable::clear(bool)
    in file db/dynamicLibrary/dlLibraryTable/dlLibraryTable.C at line 164
    Failed closing "fieldFunctionObjects" with handle 0xa8a170

In the tutorial test loop this is pure poison since output (stdout) is the input for the following changeDictionary.

For additional robustness, the warnings really should be redirected to stderr when the banner is suppressed. Additionally, loading additional libraries should likely be suppressed in foamListRegions as well. This means that the errors will disappear for that tutorial, but there still seems to be fundamental issue with the field function library.

@andy