makefile: use -buildmode=pie
makefile: use -buildmode=pie

The security benefits of PIC binaries are quite well known (since they
work with ASLR), and there is effectively no downside. In addition,
we've been seeing some weird linker errors on ppc64le that are resolved
by using -buildmode=pie.

Signed-off-by: Aleksa Sarai <a8eb12d32d6ec07cdf737175ec7d4a0f1b4e1ee7@suse.de>

jwhonce/skopeo,mtrmac/skopeo,projectatomic/skopeo,projectatomic/skopeo,mtrmac/skopeo,jwhonce/skopeo,mtrmac/skopeo