tools resolve_btfids: Always force HOSTARCH

Seth reported problem with cross builds, that fail
on resolve_btfids build, because we are trying to
build it on cross build arch.

Fixing this by always forcing the host arch.

Reported-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200923185735.3048198-2-jolsa@kernel.org