Qt6: build is not reproducible for Qt6Quick Qt6Multimedia Qt6Quick3DRuntimeRender

I was trying to see if build of Qt for Android is reproducible.

For this I made the test with Qt 6.1.3, with Android ABI x86 (NDK r22b, sdk platform 30)

Result is some binaries differ.
The lib that has the biggest difference is lib/libQt6Quick3DRuntimeRender_x86.so
The other ones have small differences

Attached if diffoscope's html output

Artifacts of diffoscope can be found here:
https://salsa.debian.org/bastif/qt-android/-/jobs/2008759

If I build a minimal standard Qt (ie not Qt for Android) build is reproducible (taken apart the other bugs I reported on that: QTBUG-96778 - QTBUG-96722 - https://bugreports.qt.io/browse/QTBUG-96778 https://bugreports.qt.io/browse/QTBUG-96722)

1st build (ie control build) was made this way:

../../configure \
 -confirm-license \
 -opensource \
 -skip qtwayland \
 --pch=no \
 -android-sdk /builds/bastif/qt-android/android-sdk \
 -android-ndk /builds/bastif/qt-android/r22b/android-ndk-r22b \
 -qt-host-path /usr/lib/qt-android-host \
 -android-abis x86 -prefix "/usr/lib/qt-android-6.1-x86" -platform android-clang \
 --ccache=yes \
 -no-warnings-are-errors \
 -- -D CMAKE_BUILD_RPATH_USE_ORIGIN=ON

Full build log is here: https://salsa.debian.org/bastif/qt-android/-/jobs/2006347

2nd build to compare was made with reprotest tool.
So in the same way, but with the variations reprotest applies

Full pipeline with all intermediate builds & artifacts can be found here:
https://salsa.debian.org/bastif/qt-android/-/pipelines/295916

Some info on reproducible builds can be found here and how to make builds reproducible

https://reproducible-builds.org/docs/