fix OpenMPI detection in CMake

CMakeLists.txt

@@ -57,9 +57,9 @@ project(ALL
 set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 
 if (CM_ALL_FORTRAN)
-    find_package(MPI REQUIRED COMPONENTS CXX Fortran)
+    find_package(MPI REQUIRED COMPONENTS C CXX Fortran)
 else()
-    find_package(MPI REQUIRED COMPONENTS CXX)
+    find_package(MPI REQUIRED COMPONENTS C CXX)
 endif (CM_ALL_FORTRAN)
 
 # Prepare the Config.cmake.in

tests/feature/CMakeLists.txt

@@ -11,15 +11,23 @@ set(OUTPUTDIR .)
 set(KNOWNGOOD ${CMAKE_CURRENT_SOURCE_DIR}/knowngood)
 # check if openmpi variable in mpi.h is set to find out, if
 # MPI version is openmpi based
-include(CheckCSourceCompiles)
- check_c_source_compiles(
-      "include <mpi.h> 
+file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/have_openmpi.c
+"#include <mpi.h>
 int main(void) {
-      #ifndef _OPENMPI
+#ifndef OPEN_MPI
 #error
 #endif
     return 0;
-      }" HAVE_OPENMPI)
+}
+")
+try_compile(HAVE_OPENMPI
+    ${CMAKE_CURRENT_BINARY_DIR}
+    ${CMAKE_CURRENT_BINARY_DIR}/have_openmpi.c
+    LINK_LIBRARIES MPI::MPI_C
+    OUTPUT_VARIABLE _try_out)
+if(NOT HAVE_OPENMPI)
+    message(FATAL_ERROR "DID NOT FIND OPENMPI\n\n${_try_out}")
+endif()
 include(FindUnixCommands)
 foreach( FEATURE
 		ALL_Staggered