Fix the tests under a Dev.xcconfig, and add smoke-test and map - #596

Run the packaged gitx tool out of a release archive, so that a bundle
whose helper cannot load the frameworks beside it fails a target here
rather than on a user's machine.

The hardened runtime is turned on for Release only, and the team
mismatch that trips library validation needs a real signing identity.
The test targets build Debug and sign ad-hoc, so nothing in the suite
assembles the configuration that ships, which is how the tool reached
users unable to load ObjectiveGit until gitx#595.

- Add smoke-test, running Contents/Resources/gitx from the archive
- Read the tool's output rather than its exit status, since it exits 1
  after printing the version either way
- Refuse a bundle without the hardened runtime, which asking for `dmg`
  in the same invocation would otherwise leave the check passing on

Read the edges out of make's own rule database, so that the answer to
which target pulls in which comes from the rules themselves and cannot
drift from them.

The help text lists eighteen targets in file order with nothing to say
which of them produces a running application, and a hand-drawn graph
would only be right until the next target arrives.

- Add scripts/make-target-map.sh, extracting the edges from `make -pnr`
  and printing each target with what it pulls in beneath it
- Add the `map` target that runs it
- Label the nodes with the help text, which stays a label rather than
  the source of the graph