Fix Clang issue for real

 - It's the tests that cause the compilation error
 - I had thought that I tested this locally, but I hadn't.

Author: zbeekman

src/CMakeLists.txt

@@ -1,9 +1,4 @@
-set(directories_to_build mpi tests)
-
-if( "${CMAKE_C_COMPILER_ID}" STREQUAL "GNU" )
-  LIST( APPEND directories_to_build iso-fortran-binding )
-endif()
-
+set(directories_to_build mpi tests iso-fortran-binding)
 foreach(directory ${directories_to_build})
   add_subdirectory(${directory})
 endforeach()

src/tests/unit/CMakeLists.txt

@@ -5,7 +5,6 @@ if (${opencoarrays_aware_compiler})
   add_subdirectory(collectives)
   add_subdirectory(sync)
   add_subdirectory(events)
-  add_subdirectory(iso-fortran-binding)
   if (gfortran_compiler)
     if(NOT CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 7)
       add_subdirectory(fail_images)
@@ -17,3 +16,6 @@ if (${opencoarrays_aware_compiler})
 else()
   add_subdirectory(extensions)
 endif()
+if( "${CMAKE_C_COMPILER_ID}" STREQUAL "GNU" )
+  add_subdirectory(iso-fortran-binding)
+endif()