Previously, touching CMakeLists.txt after a first compilation would
trigger compile errors as the two CMake runs were done with
inconsistent parameters (first one without USE_SUPERLU defined and
second one with -DUSE_SUPERLU=ON). Of course that meant that the
options would also differ from module to module, which seems like a
recipe for desaster.
This patch fixes this by moving the definition of the USE_SUPERLU
option to OpmInit.cmake which is included very early in the top most
CMakeLists.txt of each module.
ClosesOPM/opm-simulators#3908
819a28a94d