wasm: apps do not run in 5.14

Customer feedback in https://bugreports.qt.io/browse/QTBUG-63917?focusedCommentId=504598&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-504598 "Anyone can suggest which emsdk version works for multi threaded build of qt-5.14? I've tried with 1.38.30 but when running on chromium (80.0.3987.149 ) I get this: Application exit (TypeError: Cannot read property 'addEventListener' of null)

The same version of the SDK for 5.13 works for the same application I've tested (a simple Qt widget project). As to 5.14, latest release of emsdk does not build (something like fastcomp is enabled but LLVM has no support for javascript)"

<-- Difficult to understand how to setup WebAssembly as a target in Creator.