Shape with QT_QUICK_BACKEND=software crashes sometimes

From https://testresults.qt.io/logs/qt/qtlocation/932ffd6803e84fe0772df092f71414f507457bc1/LinuxUbuntu_20_04x86_64LinuxQEMUarmv7GCCqtci-linux-Ubuntu-20.04-x86_64-50-c64703Sccache_UseConfigure/7c988e7cdcc52cbb7787ae21fd3bafd39e4a79dc/test_1680307488/log.txt.gz

agent:2022/12/02 18:29:27 build.go:399: 42: PASS   : declarative_ui::MapItemsFitViewport::test_fit_circle_to_viewport(circle 1)
agent:2022/12/02 18:29:27 build.go:399: 42: qemu: uncaught target signal 11 (Segmentation fault) - core dumped

This is when running qtlocation autotests with the new Shape-based map item implementation. The ARM QEMU configurations run with QT_QPA_PLATFORM=offscreen QT_QUICK_BACKEND=software. By just setting the latter the crash is reproducable on any platform, although it will only happen from time to time.