`ar' tool from latest binutils shows warning:
ar error: `u' modifier ignored since `D' is the default (see `U')

Warning message includes word "error" so QtCreator processes it as
error in UI.

`ar' command-line option `u' might be dropped safely because it is
unnecessary. Option `c' is added to suppress extra `ar' warnings.

Other build systems are also affected. For example, automake:
https://bugzilla.redhat.com/1155273



Change-Id: Ia378b720503d93b0c0c12ae7a5f38f4d7c32eee5
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>