Allow github-act-runner as external runner

[ChristopherHX]

Currently only actions/runner and microsoft/azure-pipelines-agent are managed via --runner-version and the azpipelines event to use the ado agents.

[ChristopherHX]

./bin/Runner.Worker content for --runner-path ./

#!/usr/bin/python3
# This script can be used to call Runner.Worker as github-act-runner worker on unix like systems
# You just have to create simple .runner file in the root folder with the following Content
# {"workFolder": "_work"}
# Then use `python3 path/to/this/script.py path/to/actions/runner/bin/Runner.Worker` as the worker args

import sys
import subprocess
import os
import threading
import codecs

if sys.argv[1] != "spawnclient":
    print("Unknown command", sys.argv[1])
    sys.exit(1)
readfd = int(sys.argv[2])
writefd = int(sys.argv[3])

rdr, rdw = os.pipe()

def redirectio():
    while(True):
        messageType = int.from_bytes(os.read(readfd, 4), sys.byteorder, signed=False)
        os.write(rdw, messageType.to_bytes(4, "big", signed=False))
        messageLength = int.from_bytes(os.read(readfd, 4), sys.byteorder, signed=False)
        message = os.read(readfd, messageLength)
        encoded = codecs.decode(message, "utf_16").encode("utf-8")
        os.write(rdw, len(encoded).to_bytes(4, "big", signed=False))
        os.write(rdw, encoded)

threading.Thread(target=redirectio, daemon=True).start()

code = subprocess.call(["/path/to/github-act-runner", "worker"], stdin=rdr, stdout=sys.stdout, pass_fds=(rdr, sys.stdout.fileno()))
print(code)
# https://github.com/actions/runner/blob/af6ed41bcb47019cce2a7035bad76c97ac97b92a/src/Runner.Common/Util/TaskResultUtil.cs#L13-L14
if code == 0:
    sys.exit(100)
else:
    sys.exit(1)

[ChristopherHX]

Using both actions/runner pipe to github-act-runner stdio to actions/runner pipe works across stdio redirection. Better docker runtime than the modified actions/runner.