WebAssembly build fails during qt5.git integration in '5.15'

Continuous Integration: Failed

The configure script returned an error. The CI rejected the staged commits due to the beforementioned reason. Possible reason could be a bug in one of the commits or some more recent change. Please investigate it.

The error was in "qt/qt5", revision: 51d0a3e7e410045dbfd367e7ebf7a7d6c0b263af

Build log: https://testresults.qt.io/logs/qt/qt5/183aea75a9c3516061aabfe55b933cd621551917/WindowsWindows_10x86_64WindowsWebAssemblyx86_64Mingw73qtci-windows-10-x86_64-15-f36aa5DisableTests/2d87d453f29cdd5a2a04fc14020d55ca38676153/build_1580797464/log.txt.gz

Details: https://testresults.qt.io/coin/integration/qt/qt5/tasks/1580797462
Tested changes (refs/builds/qtci/5.15/1580796184):
https://codereview.qt-project.org/c/qt/qt5/+/288302 Update submodules on '5.15' in qt/qt5