Apply suggestions from code review

Author: JarLob

cpp/ql/src/experimental/Security/CWE/CWE-266/IncorrectPrivilegeAssignment.ql

@@ -55,10 +55,11 @@ where
     ) and
     (
       fctmp.getArgument(1).getValue().matches("%a%") or
+      fctmp.getArgument(1).getValue().matches("%w%") or
       // unfortunately cannot use numeric value here because // O_APPEND is defined differently on different OSes:
       // https://github.com/red/red/blob/92feb0c0d5f91e087ab35fface6906afbf99b603/runtime/definitions.reds#L477-L491
       // this may introduce false negatives
-      fctmp.getArgument(1).getValueText().matches("%O_APPEND%")
+      fctmp.getArgument(1).(BitwiseOrExpr).getAChild*().getValueText().matches("O_CREAT")
     ) and
     fctmp.getNumberOfArguments() = 2 and
     not fctmp.getArgument(0).getValue() = "/dev/null" and