libI810XvMC is built on all architectures, wether it is sensible or not

[Mike A. Harris]

The libI810XvMC library is an XvMC hardware driver for Intel
integrated video.  This is built on PPC and other architectures
when XvMC is built, even though Intel video isn't available for
those architectures, and isn't likely to ever be available on
them.  This should only be built on x86, and if it is known
to be 64bit clean and work on ia64 and amd64, then it should
probably be built on them too, as Intel video is available on
those 3 platforms at least.  It should not be built on PPC/PPC64
and s390 variants, nor Alpha/Sparc/etc.

Examining the problem, the XvMC makefile just builds all
subdirs including the i810 XvMC driver regardless of architecture.

The short distribution packaging fix is to just delete the
file on non-x86 arch, but I think it should be fixed in the
X.Org CVS tree more correctly.  I'm just not sure what the
best solution is, but I have some thoughts.

An easy fix, would be to just add arch conditionals directly
in the xc/libs/XvMC/Imakefile so it only hits the i810 dir
on x86 (and possibly ia64/amd64).  That's quick and easy, but
a bit of a quick one time hack, which wont scale should we
get more drivers in the future for other hardware IMHO.

I better fix I'm thinking, would be to add XvMCDrivers and
XvMCDriversDevel directives to xorg.cf per architecture, and
default it to "i810" on x86 (and maybe ia64/amd64), but leave
it defined to "/* */" on all other architectures since there
are no drivers for them.

Then modify the XvMC Imakefile to use the new directives when
determining what dirs to process.

Does this sound sensible?  If so I'll file it in bugzilla, and
we can track it there.