dpkg: use homebrew gtar in C programs

dpkg will call tar with options like --warning=no-timestamp, which OSX's
tar does not support.  We should specify TAR=gtar to ./configure so
things like dpkg-scanpackages use the correct tar.

Signed-off-by: Drew Fisher <zarvox@zarvox.org>

Closes #29074.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>