> Renato Silva added the comment:
>
> I must note that GCC 4.x *does* support -mno-cygwin, at least until 4.4,
and at least the MinGW version.

MinGW has never "supported" the -mno-cygwin option. It has simply tolerated
it. The option never did anything useful and at some point it became an
error to even supply it. I'm not sure exactly when but some time after 4.4
sounds reasonable to me.

The option was only ever meaningful in cygwin's gcc 3.x and was always an
error in 4.x.

> I have used it myself for building Pidgin under Windows, which requires
that option. See [1] where a Pidgin developer confirms that.
>

No the developer does not confirm that the -mno-cygin option is required
for MinGW. Also from what I've seen I would say that the error message that
the OP shows there comes from Cygwin's gcc not MinGW.