QT_ANDROID_EXTRA_LIBS ignored for secondary ABIs

When building an Android project using CMake for multiple ABIs, the QT_ANDROID_EXTRA_LIBS target property is only taken from the main ABI being build, but values set in secondary ABI builds are ignored.

As a workaround it is possible to specify extra libraries for all ABIs, and Qt is smart enough to only take the libraries for the ABIs that are being build. If this is expected behavior it should at least be documented, but I think the correct behavior would be for the value to be taken from all ABI builds.

Attached is a sample project reproducing the issue. To reproduce:

1. Build the project for Android with QT_ANDROID_BUILD_ALL_ABIS=ON.
2. Check the "bundled_libs" array in android-build/res/values/libs.xml in the build folder.

Expected: should contain iconv for all 4 ABIs.

Actual: contains libiconv only for the main ABI (e.g. "arm64-v8a;iconv")