Fix typo in CMakeLists

Author: ntselepidis

CMakeLists.txt

@@ -20,7 +20,7 @@ option(MFC_MPI           "Build with MPI"                                     ON
 option(MFC_OpenACC       "Build with OpenACC"                                OFF)
 option(MFC_GCov          "Build with GCov"                                   OFF)
 option(MFC_Unified       "Build with unified CPU & GPU memory (GH-200 only)" OFF)
-option(MFC_Fastmath      "Build with -fastmath on NV GPUs"                   OFF)
+option(MFC_Fastmath      "Build with -gpu=fastmath on NV GPUs"               OFF)
 option(MFC_PRE_PROCESS   "Build pre_process"                                 OFF)
 option(MFC_SIMULATION    "Build simulation"                                  OFF)
 option(MFC_POST_PROCESS  "Build post_process"                                OFF)