tst_qtiff failures in qt5.git#5.15

agent:2020/03/11 11:01:07 build.go:253: FAIL! : tst_qtiff::readWriteNonDestructive(tiff rgb32) Compared values are not the same
agent:2020/03/11 11:01:07 build.go:253: Loc: [tst_qtiff.cpp(440)]

Build log: http://10.212.3.36:8080/coin/api/results/qt/qtimageformats/5d0c2938d6940f0f1fbbb73c9155c7502d042c30/MacOSMacOS_10_13x86_64MacOSMacOS_10_13x86_64Clangqtci-macos-10.13-x86_64-2-dc4a1e/5f20449ca3c4cdb6cb4356153d738a19560f8136/test_1583924090/log.txt.gz

Details: http://10.212.3.36:8080/coin/integration/qt/qt5/tasks/1583923756
Tested changes (refs/builds/qtci/5.15/1583880496):
https://codereview.qt-project.org/c/qt/qt5/+/292969 Update submodules on '5.15' in qt/qt5