Fix missing INCLUDE_DIRECTORIES, missing SYSTEM from merge

CMakeLists.txt

@@ -315,6 +315,10 @@ INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR})
 
 # Build active components. Add utilities and solvers directories first, because
 # that allows us to detect library dependencies automatically.
+IF (NEKTAR_BUILD_LIBRARY)
+    INCLUDE_DIRECTORIES(library)
+ENDIF()
+
 INCLUDE_DIRECTORIES(utilities)
 ADD_SUBDIRECTORY(utilities)
 
@@ -325,7 +329,6 @@ IF (NEKTAR_BUILD_LIBRARY)
     # List of Nektar++ libraries will be rebuilt every configuration.
     SET(NEKTAR++_LIBRARIES "" CACHE INTERNAL "")
 
-    INCLUDE_DIRECTORIES(library)
     ADD_SUBDIRECTORY(library)
     INSTALL(EXPORT Nektar++Libraries DESTINATION ${LIB_DIR}/cmake COMPONENT dev)
 ENDIF (NEKTAR_BUILD_LIBRARY)

cmake/ThirdPartyMPI.cmake

@@ -32,7 +32,7 @@ IF( NEKTAR_USE_MPI )
                 SET(BUILD_MPI ON)
             ELSE()
                 MARK_AS_ADVANCED(file_cmd)
-                INCLUDE_DIRECTORIES(${MPI_CXX_INCLUDE_PATH})
+                INCLUDE_DIRECTORIES(SYSTEM ${MPI_CXX_INCLUDE_PATH})
                 MESSAGE(STATUS "Found MPI: ${MPI_CXX_LIBRARIES}")
             ENDIF()
         ENDIF()