Use the alpine base image and install the tools to compile
tini manually. This removes the dependency on c-compile.
Also use the git tree hash for the package hash while at it.
Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Previously the "tini" contained the entire build. Using the
multi-stage build creates a new "tini" base image, which only
contains the "/bin/tini". This image can be used as the base
image for packages requiring "tini".
Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
