QSR runtime test cases fails on MIPS target

Steps to reproduce:

0) Prepare VM 

Use this commit to build the QSR for the QEMU MIPS64:

https://codereview.qt-project.org/c/tqtc-boot2qt/qtsaferenderer/+/267221

Check the Save VM on failure tick and try to build.

1) install static MIPS QEMU

sudo apt install qemu-user-static

2) Set env

export QEMU_LD_PREFIX=/opt/yocto-mips64/sysroots/mips64-poky-linux

export QT_QPA_PLATFORM=offscreen

3) Run the test case
qt@10-215-195-11:~/work/build/tests$ qemu-mips64-static ./tst_qsaferenderer

Start testing of SafeRenderer::tst_QSafeRenderer *********
Config: Using QtTest library 5.15.1, Qt 5.15.1 (mips64-big_endian-lp64-n64-hardfloat shared (dynamic) release build; by GCC 8.2.0), b2qt 2.6.1
qemu: Unsupported syscall: 5326
qemu: Unsupported syscall: 5326
PASS : SafeRenderer::tst_QSafeRenderer::initTestCase()
FAIL! : SafeRenderer::tst_QSafeRenderer::testSafeLayoutReaderOK() Caught unhandled exception
Loc: [qtestcase.cpp(1939)]
Totals: 1 passed, 1 failed, 0 skipped, 0 blacklisted, 128ms

Finished testing of SafeRenderer::tst_QSafeRenderer *********
terminate called after throwing an instance of 'SafeRenderer::QSafeLayout::LayoutException'
qemu: uncaught target signal 6 (Aborted) - core dumped