dashboard/app: provide self-contained repro scripts

[dvyukov]

Reflecting on the syzbot experience, some developers say that the reproducers don't reproduce bugs for them. There are probably some differences in setup or something, because in most cases I can reproduce these bugs locally in qemu. It would be useful to generate scripts that will do all necessary setup (e.g. checking out kernel, building it with the right compiler and config, starting qemu with the right image, etc) and trigger the bug. This can be especially useful for syzkaller reproducers as they are harder to run (we could provide all necessary flags for syz-execprog too).

[dvyukov]

Mark Rutland suggested that this script also needs an option to accept a custom kernel (that a developer built themselves). Which is reasonable for debugging/fix testing.

[lag-linaro]

Bump.

Either this or please unify the URLs to a Dashboard Reports artifacts so we can author our own simple get/play scripts.

Currently, links to the .config and c-repro are un-derivable and enact redirects which curl -L seems to have trouble with.