package/tini: compile executable static

package/tini: compile executable static

One usecase for tini is as the init process for a container which has
a single executable and no C runtime library. It therefore needs to be
independent of any C runtime library within the container.

Previously, we didn't build statically to avoid problems with
BR2_SHARED_LIBS=y. However, it turns out that tini can successfully link
statically even with glibc and BR2_SHARED_LIBS=y, because libc.a is
still included in staging, and tini doesn't use any NSS functionality.

Signed-off-by: Simon Rowe <simon.rowe@citrix.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>