Crash in V4 engine on ARM32

Reincarnation of --QTBUG-55561--. Reported by our potential customers who have been evaluating Qt on a Nvidia Tegra K1 device.

A bus error cased by
1) Any directory or JS import statement in a QML file running in a QQuickView;
2) New'ing any raw object in JavaScript. Remove the property foo, and the bus error goes away.

import QtQuick 2.0

Item {
    id: root
    property var foo: {
        var f = {};
        return f;
    }
}

Running GDB

(gdb) run
Starting program: /root/openglunderqml
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
[New LWP 654]
[New LWP 655]

Thread 3 "QQmlThread" received signal SIGBUS, Bus error.
[Switching to LWP 655]
0xb61b9cd0 in QV4::Compiler::JSUnitGenerator::writeFunction(char*, QV4::IR::Function*) const () from /usr/lib/libQt5Qml.so.5

This function is in qtdeclarative/src/qml/compiler/qv4compiler.cpp line 280.
Rerunning with a breakpoint on that function, here is the backtrace

(gdb) backtrace
#0  0xb610d158 in QV4::Compiler::JSUnitGenerator::writeFunction(char*, QV4::IR::Function*) const@plt () from /usr/lib/libQt5Qml.so.5
#1  0xb613b700 in QV4::Compiler::JSUnitGenerator::generateUnit(QV4::Compiler::JSUnitGenerator::GeneratorOption) () from /usr/lib/libQt5Qml.so.5
#2  0x03189cb0 in ?? ()

It looks like an alignment issue where the argument f in writeFunction (which is cast to a QV4::CompiledData::Function) isn't on an 8-byte boundary.

Initially reported for 5.8.0 (that already included this fix), then they confirmed this is also reproducible with 5.9.0 (they are building Qt as part of their custom buildroot, if that makes any difference).