Hey midiosh,
yes, you need to build on a mac. Otherwise you need to cross compile. But cross compilation from windows to macos is not possible, never heard of that.
Cross compilation does work though with the VST3 SDK. If you build for Android (which is not supported yet but still, it is possible with some tweaks), run a Linux Ubuntu, get the Android SDK which contains an Android toolchain and build for Android successfully. The toolchain contains all the necessary libraries and compilers needed.
Does it answer your question?
Cheers,
René