clang compiler crashes in CI

There are various crashes in CI of the clang compiler on Android and iOS integrations (see errors at

https://codereview.qt-project.org/c/qt/qtdeclarative/+/338349,

https://codereview.qt-project.org/c/qt/qtdeclarative/+/338335;

direct link to log: https://testresults.qt.io/logs/qt/qtdeclarative/04c5d90807221af5a13139808a0a0d1a5f162dfd/MacOSMacOS_10_14x86_64IOSIOS_ANYarm64Clangqtci-macos-10.14-x86_64-93139aDebugAndRelease_Sccache/4964ef18e52f4b0c6e120a7f8c5be8a3431d0f1c/build_1615533484/log.txt.gz)

iOS failed job
https://testresults.qt.io/coin/integration/qt/qt5/tasks/1616103354

Android failed job
https://testresults.qt.io/coin/integration/qt/qtdeclarative/tasks/1615645573

This seems to be completely unrelated to the actual change that is integrating.