meson: don't require libelf for r600 without LLVM

r600 doesn't have a hard requirement on LLVM, and therefore doesn't have
a hard requirement on libelf. Currently the logic doesn't allow that
however.

Distro-bug: https://bugs.gentoo.org/669058
Fixes: 5060c51b6f4dfb0d5358bde6523285163d3faaad
       ("meson: build r600 driver")
Reviewed-by: Matt Turner <mattst88@gmail.com>
1 file changed