Steps:
1. Create qt project with qbs build system and msvc compiler.
2. Give own compiler flag "/Zm300" to cpp.cxxFlags property.
Actual result:
There is few warnings:
"D9025 overriding '/Zm200' with '/Zm300' and
"D9025 overriding '/Zm200' with '/Zm300'.

Build crashes due to lack of virtual memory (cause 'Zm200' flag hardcoded in core.qbs).

Expected result:
There is possibility to give compiler own '/Zm' flag