This reverts commit cbe0f44c4f7bc3715acbf148f981bd93111c4c8f.
This achieves the same result as the reverted commit wrt. process in the
same manner (writing a keepalive into the socket and checking if it
failed to send). However, it does _not_ allow the process to die on
reaching pipe EOF, since this can cause many spams of subprocesses when
stdin is actually not a tty (e.g. in a Docker container).
these weren't getting corrected since php-cs-fixer 3.0 due to a change in the default configuration for native_function_invocation. Since the builds are randomly choosing to use php-cs-fixer 2.19 at the moment, the consistency is a problem.
this happens if the parent process is killed via SIGINT, because its stdin will be closed, interrupting a blocking read. This might also happen if the user pressed CTRL+D, so we don't die unless end of socket stream was also detected.
closes#4335
