QCommandLineOption: prevent aggressive inlining

Even though we expect very few option names, GCC unrolls the
loop calling IsInvalidName::operator() four times. Together
with the lead-in/lead-out for size() % 4 != 0, that makes
for five inlined copies of the function call operator.

I don't know how to prevent the unrolling, but at least I can
stop the inlining.

Change-Id: Ib9d6c33e8193464a73927a92b8b54c3452cb26a3
Reviewed-by: David Faure <david.faure@kdab.com>

src/corelib/tools/qcommandlineoption.cpp

@@ -250,6 +250,7 @@ namespace {
         typedef bool result_type;
         typedef QString argument_type;
 
+        Q_NEVER_INLINE
         result_type operator()(const QString &name) const Q_DECL_NOEXCEPT
         {
             if (Q_UNLIKELY(name.isEmpty()))