[FFmpeg-devel] handle carriage returns in cleanws()

[俞晓磊]

When configuring ffmpeg in a cygwin shell for a non-cygwin toolchain,
the generated cc_ident contains a carriage return, which is propagated
into config.h.
The cause seems to be that cygwin treats carriage return as a normal character.
I can workaround this by adding 's/\r//' to cleanws' sed command in a
patching step.

I don't know whether cygwin + non-cygwin toolchain is supported by
ffmpeg, but it would be nice if cleanws removes '\r' by default.