This are the steps to be done for configuring a mac for being a build slave to the Kodi jenkins CI system
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1. setup user jenkins as follows:

# create jenkins group
NEXT_GID=$((`dscl /Local/Default list /Groups gid | awk '{ print $2 }' | sort -n | grep -v '^[5-9]' | tail -n1` + 1))
sudo dscl /Local/Default create /Groups/jenkins
sudo dscl /Local/Default create /Groups/jenkins PrimaryGroupID $NEXT_GID
sudo dscl /Local/Default create /Groups/jenkins Password \*
sudo dscl /Local/Default create /Groups/jenkins RealName 'Jenkins Node Service'
# create jenkins user
NEXT_UID=$((`dscl /Local/Default list /Users uid | awk '{ print $2 }' | sort -n | grep -v '^[5-9]' | tail -n1` + 1))
sudo dscl /Local/Default create /Users/jenkins
sudo dscl /Local/Default create /Users/jenkins UniqueID $NEXT_UID
sudo dscl /Local/Default create /Users/jenkins PrimaryGroupID $NEXT_GID
sudo dscl /Local/Default create /Users/jenkins UserShell /usr/bin/false
sudo dscl /Local/Default create /Users/jenkins NFSHomeDirectory /var/lib/jenkins
sudo dscl /Local/Default create /Users/jenkins Password \*
sudo dseditgroup -o edit -a jenkins -t user jenkins
# create the jenkins home dir
sudo mkdir /var/lib/jenkins
sudo chown -R jenkins:wheel /var/lib/jenkins
# create a logging space
sudo mkdir /var/log/jenkins
sudo chown jenkins:wheel /var/log/jenkins

3. mkdir /Users/Shared/jenkins

4. sudo chown jenkins:wheel /Users/Shared/jenkins

5. mkdir -p /Users/Shared/xbmc-depends/dSyms

6. sudo chown -R jenkins:wheel /Users/Shared/xbmc-depends/

7. Change to user jenknis via sudo -u jenkins bash

8. mkdir /Users/Shared/jenkins/slave

9. nano /Users/Shared/jenkins/slave/startslave.sh and add the following

#!/bin/sh

rm error.log
rm stdout.log
java -Djava.awt.headless=true -jar slave.jar -jar-cache /Users/Shared/jenkins/cache -jnlpUrl http://jenkins.kodi.tv/computer/<node name from jenkins node page>/slave-agent.jnlp -secret <secret from jenkins node page>

10. chmod +x /Users/Shared/jenkins/slave/startslave.sh

11. edit startslave.sh and add nodename and the secret at the end of the command line from the node page

12. nano /Users/Shared/jenkins/slave/org.jenkins-ci.slave.jnlp.plist and add the following

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.example.ci</string>
    <key>ProgramArguments</key>
    <array>
        <string>/Users/Shared/jenkins/slave/startslave.sh</string>
    </array>
    <key>KeepAlive</key>
    <true/>
    <key>RunAtLoad</key>
    <true/>
    <key>SessionCreate</key>
    <true/>
    <key>UserName</key>
    <string>jenkins</string>
    <key>WorkingDirectory</key>
    <string>/Users/Shared/jenkins</string>
    <key>StandardOutPath</key>
    <string>/Users/Shared/jenkins/slave/stdout.log</string>
    <key>StandardErrorPath</key>
    <string>/Users/Shared/jenkins/slave/error.log</string>
</dict>
</plist>

13. sudo mv /Users/Shared/jenkins/slave/org.jenkins-ci.slave.jnlp.plist /Library/LaunchDaemons/org.jenkins-ci.slave.jnlp.plist

14. sudo nano /etc/profile and add PATH=$PATH:/usr/local/bin

15. curl http://jenkins.kodi.tv/jnlpJars/slave.jar -Lo /Users/Shared/jenkins/slave.jar

16. install java JDK 8

17. Install Xcode (get it from developer.apple.com -> Downloads) and start it once (accept license):
- 10.2 to /Applications/Xcode10.2.app - for macOS and iOS builds
- 11.3.1 to /Applications/Xcode11.3.1.app - for tvOS builds

18. install brew

19. install ccache via brew (brew install ccache)

20. edit /var/lib/jenkins/.ccache/ccache.conf and set max_size to 20.0G (this file might just appear after the first build done on the node)

21. load service:
sudo launchctl load /Library/LaunchDaemons/org.jenkins-ci.slave.jnlp.plist