qmake creates nondeterministic results

While working on reproducible builds for openSUSE, I found that
when building the libqt5-qttools package, there were differences between each build.
/usr/lib64/libQt5Designer.so.5.15.1 differs in ELF section .rodata

Results do not differ when using a filesystem with deterministic readdir order.

maybe because

src/corelib/io/qfilesystemiterator_unix.cpp used readdir (2) via QT_READDIR

various Makefiles showed differing ordering of .pri entries

qrc_SmartPhoneWithButtons.cpp has varying order of embedded .png files from rcc.