build: fix default config
build: fix default config

Apparently gst_structure_from_string() doesn't like the multiple lines
in omx_mpeg4dec caps.

It's easily fixable by passing the -P option to the preprocessor, which
also gets rid of the comments.

If this breaks with somebody's pre-processor, speak now :)

Reported-by: Sebastian Dröge <e285265cec5086eaacf9a8100f9a52e9fd479a5e@circular-chaos.org>
Signed-off-by: Felipe Contreras <de77a8b9cd239b204c19c52ed62e48ab47243362@gmail.com>

freedesktop-unofficial-mirror/gstreamer__attic__gst-openmax,matsu/gst-openmax,matsu/gst-openmax,freedesktop-unofficial-mirror/gstreamer__attic__gst-openmax