This is a quick blog post in order to set things straight. Though all major results from google pointing to the contrary (that linux is uninstallable on a sparc machine) these days I came to a fully functional 480 server while using gentoo sparc autobuilds. Other linux distros (debian,redhat,centos,suse) could not even boot the machine :S
So gentoo is your friend.
If for any reason anyone is intrested on the specifics of the “operation” please write a follow up 
...
configure: Using system-installed FFMpeg code
configure: WARNING:
======================================================================
WARNING: you have chosen to build gst-ffmpeg against a random
external version of ffmpeg instead of building it against the tested
internal ffmpeg snapshot that is included with gst-ffmpeg.
This is a very bad idea. So bad in fact that words cannot express
just how bad it is. Suffice to say that it is BAD.
The GStreamer developers cannot and will not support a gst-ffmpeg
built this way. Any bug reports that indicate there is an external
version of ffmpeg involved will be closed immediately without further
investigation.
The reason such a setup can't be supported is that the ffmpeg API
and ABI is in constant flux, yet there aren't any official releases
of the ffmpeg library to develop against. This makes it impossible
to guarantee that gst-ffmpeg will work reliably, or even compile,
with a randomly picked version ffmpeg. Even if gst-ffmpeg compiles
and superficially appears to work fine against your chosen external
ffmpeg version, that might just not be the case on other systems, or
even the same system at a later time, or when using decoders,
encoders, demuxers or muxers that have not been tested.
Please do not create or distribute binary packages of gst-ffmpeg
that link against an external ffmpeg. Thank you!
======================================================================
checking for sed... /bin/sed
...
LOL that’s what I call programmers with humor 
And of course build succeeds and ffmpeg packages works alright