help: add shell-path to --build-options
It may be useful to know which shell Git was built to try to point to,
in the event that shell-based Git commands are failing. $SHELL_PATH is
set during the build and used to launch the manpage viewer, as well as
by git-compat-util.h, and it's used during tests. 'git version
--build-options' is encouraged for use in bug reports, so it makes sense
to include this information there.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>