https://bugreports.qt.io/browse/QTBUG-87735
bug fixed)
Fix Version/s: 6.0.0 RC

Hi Patrick. I'm in the same situation. Installation on archlinux using the official qt5.13 online installer. Android and desktop kits are well configured on qtcreator just by using their respectif qmake. However when I choose the one.of webassembly (wasm_32) distributed by qt, qtcreator warns about the ABI, saying that it is not defined. Its value is unknown-unknown-unknown-.....

I compiled a simple qt project using wasm_32 kit but link fails with the following error main.o: architecture machine must be wasm32.

Any help?

Did you install Xcode 8 ?

Your other error comes from the fact that you are calling xcodebuild in the folder where it's located and not where a Xcode project can be found.