devops: fix protocol generation with root on Linux

[mxschmitt]

Currently it was leading to an error if I tried to build it with a root user on a Linux environment. So in the end the type generation was just skipped:

22:51:55.757 $ node install-from-github.js
22:51:55.813 Building playwright...
22:52:14.094 chromium downloaded to /11994741/playwright/.local-chromium/linux-747023 22:52:14.123 Failed to launch browser!
22:52:14.123 [0310/215214.121201:ERROR:zygote_host_impl_linux.cc(89)] Running as root without --no-sandbox is not supported. See https://crbug.com/638180.
22:52:14.123 TROUBLESHOOTING: https://github.com/Microsoft/playwright/blob/master/docs/troubleshooting.md

Maybe we should also exit the script with an error code if the protocol generation was not successful.

[aslushnikov]

@mxschmitt Thanks!