The upcoming dwarves host package requires elfutils. As dependencies for
tools must exist in tools, we need to move elfutils host build there.
As there is at least one package that depends on this, and there is no
proper way to create such dependency in the build system, build it
unconditionally when not building on macOS.
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
