Upgrade cloudabi-utils to version 0.5.

CloudABI now has its own package collection for FreeBSD and Debian based
systems (https://github.com/NuxiNL/cloudabi-ports/). This package
collection will only contain software that is cross compiled for
CloudABI -- no FreeBSD native executables.

I would like to go ahead and remove all ports that overlap with the
packages provided by CloudABI Ports. Let's start off by updating
cloudabi-utils to version 0.5. This version no longer depends on the
CloudABI toolchain, as it now ships with a precompiled copy of the
trampoline executable.

Once this is done, I can go ahead and remove devel/cloudabi-cloudlibc,
devel/cloudabi-compiler-rt, devel/cloudabi-libc++,
devel/cloudabi-libc++abi and devel/cloudabi-libunwind/.

Approved by: bapt
Differential Revision: https://reviews.freebsd.org/D3616