CMake: Remove unused wall option when FC=flang

cmake/fc.cmake

@@ -5,13 +5,8 @@
 
 if (${F_COMPILER} STREQUAL "FLANG")
   set(CCOMMON_OPT "${CCOMMON_OPT} -DF_INTERFACE_FLANG")
-  if (BINARY64)
-    if (INTERFACE64)
-      set(FCOMMON_OPT "${FCOMMON_OPT} -i8")
-    endif ()
-    set(FCOMMON_OPT "${FCOMMON_OPT} -Wall")
-  else ()
-    set(FCOMMON_OPT "${FCOMMON_OPT} -Wall")
+  if (BINARY64 AND INTERFACE64)
+    set(FCOMMON_OPT "${FCOMMON_OPT} -i8")
   endif ()
   if (USE_OPENMP)
     set(FCOMMON_OPT "${FCOMMON_OPT} -fopenmp")