Build fix for -developer-build with certain features disabled

When building with -developer-build the unused-parameter warning is
 a build breaker error, but some combinations of -no-features was
 still making it happen.

Change-Id: Ib6354e6a599b8d64fd593fb94e9cfa32db63c77d
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/io/qfilesystemiterator_unix.cpp

@@ -86,6 +86,8 @@ static bool checkNameDecodable(const char *d_name, qsizetype len)
     return cs.invalidChars == 0 && cs.remainingChars == 0;
 #else
     // if we have no text codecs, then QString::fromLocal8Bit is fromLatin1
+    Q_UNUSED(d_name)
+    Q_UNUSED(len)
     return true;
 #endif
 }