Use F_COMPILER name

Author: mathomp4

cmake/system.cmake

@@ -382,7 +382,7 @@ if (NEED_PIC)
   if (NOT NOFORTRAN)
     if (${F_COMPILER} STREQUAL "SUN")
       set(FCOMMON_OPT "${FCOMMON_OPT} -pic")
-    elseif (${F_COMPILER} STREQUAL "NAG")
+    elseif (${F_COMPILER} STREQUAL "NAGFOR")
       set(FCOMMON_OPT "${FCOMMON_OPT} -PIC")
     else ()
       set(FCOMMON_OPT "${FCOMMON_OPT} -fPIC")