devel/libuv: Use upstream release archive with GNU Autotools files pre-generated

Upstream offers a distfile with GNU Autotools files pre-generated which
saves quite a bit of time as USES= autoreconf pulls in Perl and a few
other deps. This speeds up initial bootstrapping when we need to build
CMake for example.

Thanks to bofh for some advice about this

PR: 274622
Reviewed by: adamw (maintainer)