fixed: we need to do mpi disabling earlier

if not, prereqs do not see this file, and the option ends
up not being operational for prereqs looking for MPI.

cmake/Modules/OpmInit.cmake

@@ -74,3 +74,10 @@ if (USE_VERSIONED_DIR)
 else ()
   set (${project}_VER_DIR "")
 endif ()
+
+# parallel computing must be explicitly enabled
+# This needs to be in OpmInit as prereqs is called before OpmLibMain is included.
+option (USE_MPI "Use Message Passing Interface for parallel computing" OFF)
+if (NOT USE_MPI)
+  set (CMAKE_DISABLE_FIND_PACKAGE_MPI TRUE)
+endif ()

cmake/Modules/OpmLibMain.cmake

@@ -90,12 +90,6 @@ include (UseOptimization)
 # dependencies, in case they alter the list of warnings
 include (UseWarnings)
 
-# parallel computing must be explicitly enabled
-option (USE_MPI "Use Message Passing Interface for parallel computing" OFF)
-if (NOT USE_MPI)
-	set (CMAKE_DISABLE_FIND_PACKAGE_MPI TRUE)
-endif (NOT USE_MPI)
-
 # parallel programming
 include (UseOpenMP)
 find_openmp (${project})