[CMake] include a Stokes process module.

ProcessLib/StokesFlow/CMakeLists.txt

+get_source_files(SOURCES)
+
+ogs_add_library(StokesFlow ${SOURCES})
+
+target_link_libraries(StokesFlow PUBLIC ProcessLib PRIVATE ParameterLib)
+
+if(OGS_BUILD_TESTING)
+    include(Tests.cmake)
+endif()

scripts/cmake/ProcessesSetup.cmake

@@ -2,6 +2,7 @@
 # processes to be build.
 set(_processes_list
     ComponentTransport
+    StokesFlow
     HT
     HeatConduction
     HeatTransportBHE