[PATCH v2 1/1] ci(osx): use new location of the `perforce` cask

From: Johannes Schindelin <johannes.schindelin@gmx.de>

The CI builds are failing for Mac OS X due to a change in the location of the perforce cask. The command outputs the following error:

    + brew install caskroom/cask/perforce
    Error: caskroom/cask was moved. Tap homebrew/cask-cask instead.

So let's try to call `brew cask install perforce` first (which is what that error message suggests, in a most round-about way).

The "caskroom" way was added in 672f51cb (travis-ci: fix Perforce install on macOS, 2017-01-22) and the justification is that the call "brew cask install perforce" can fail due to a checksum mismatch: the recipe simply downloads the official Perforce distro, and whenever that is updated, the recipe needs to be updated, too.

CI servers are typically fresh virtual machines, but not always. To accommodate for that, let's try harder if `brew cask install perforce` fails, by specifically pulling the latest `master` of the `homebrew-cask` repository.

This will still fail, of course, when `homebrew-cask` falls behind Perforce's release schedule. But once it is updated, we can now simply re-run the failed jobs and they will pick up that update.

As for updating `homebrew-cask`: the beginnings of automating this in https://dev.azure.com/gitgitgadget/git/_build?definitionId=11&_a=summary will be finished once the next Perforce upgrade comes around.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 ci/install-dependencies.sh | 5 +++++
 1 file changed, 5 insertions(+)