Compiling against single precision OpenFOAM leads to undefined symbol errors

[greole]

Currently, we only support DP scalars. Compiling against SP OpenFOAM leads to the following error.

v2312/platforms/linux64GccSPInt32Opt/lib/libOGL.so: undefined symbol: _ZNK4Foam9lduMatrix6solver11scalarSolveERNS_5FieldIdEERKS3_h

A workaround is to modify the CMakeLists.txt and set

  target_compile_definitions(OGL PUBLIC WM_LABEL_SIZE=32 WM_ARCH_OPTION=32
              NoRepository WM_SP)

here the important bit is to set WM_SP since this will be used with #ifdef macros to set the scalar type in scalar.H. Eventually this should be done automatically by cmake, by reading$WM_LABEL_SIZE and $WM_PRECISION_OPTION.