After looking around, I could not find a single CI tool that would make builds for multiple OS's. Is there an overview of which tools support which? Is there a tool that supports multiple in the first place? (Like Travis supports OSX/Linux)
Thanks in advance!
Jenkins is an open-source, multi-platform CI system. It runs on top of Java, so you can run build agents (and the master server) where-ever Java is available.
I use it successfully for over a year to build projects on Linux and Windows platforms (including complex build flows that require build/test steps on both platforms for a single project).
Jenkins also has hundreds of plugins, many of them are actively developed by the community.