Check whether bazelisk installed

[Leo7654]

If bazelisk-version is not given, this action does not download bazelisk without notice.

So check whether bazelisk installed after setting up bazelisk(bazel).

[p0deje]

GitHub Actions runners come with bazelisk installed, that's why it's not installed when specific version is requested via bazelisk-version. How would you prefer it to work?

[Leo7654]

Thank you for response. I am using on-premise runner. It was hard to notice that bazelisk has not been installed.
I think it should be failed if bazelisk is not installed.

[p0deje]

Why? It's perfectly fine just to use bazel directly if it's preinstalled. You might want to opt-in to use bazelisk, but it's not a hard requirement.

[Leo7654]

I mean it is hard to notice bazel or bazelisk is installed or not.
Actually, setup-bazel action does not setup bazel if 'bazelisk-version' is not given by default.

[p0deje]

Fair enough, I agree that the action should check for bazelisk or bazel to be installed and, if both are missing, it should install bazelisk. I will gladly merge a PR adding this support.