update.sh: only update to semver tags.

tests: speed up integration tests coverage

Otherwise random e.g. `pr-123` tags may cause `brew update` to update
to the wrong version.

sandbox: tweak HOMEBREW_REPOSITORY handling.

Previously, .simplecov called `SimpleCov.result` to store the coverage
result, and ignored the return value. `SimpleCov.result`'s return can be
slow to calculate, which wastes a lot of time when it's ignored.

This commit extracts the code needed to store the SimpleCov result from
`SimpleCov.result`, and calls it directly, without doing the busywork to
compute the return value every time.

In my testing, this more than halves the time taken to run all the
integration tests.

Remove old cctools references now that only ruby-macho is used.

Fix coverage reporting.

dependency_collector: Fix ant_dep for Linux