If Tini is built without its own .git directory, but within another
git directory (i.e. the tarball was extracted in a directory
that happens to be a git tree), then we end up with the wrong
git version in `tini -h`.
This actually happens in the Alpine builds (e.g. Tini 0.8.3 in
Alpine has git hash d89e144, which is a Aports commit hash, not
a Tini commit hash:
https://github.com/alpinelinux/aports/commit/d89e144
This patch forces git to use the current git directory, or to not
use one at all (which is fine, since in that case Tini is
presumably being built from a release tarball).
Some platforms (Alpine Linux being one) define _FORTIFY_SOURCE
as a built-in. Redefining it causes a compilation error since we
treat warnings as errors.
Fixes: #22
This allows the use of `tini` within even more minimal environments (such as images that are `FROM scratch` with a single application binary `COPY`'d in).