Qt app compiled for M1 Apple marked as damaged

Using an m1 Mini I've built Qt 5.15 and everything's good except for two issues:

First, when I qmake a a pro file from the command-line the resulting Makefile has EXPORT_VALID_ARCH = x86_64. I did compile Qt with QMAKE_APPLE_DEVICE_ARCHS=arm64.

If I manually change the Makefile to EXPORT_VALID_ARCH = arm64 the compile completes w/o errors giving me an arm64 binary.

Next, when the app packaged as a zip or dmg is downloaded from my website It's marked as damaged and macOS advises its deletion. This can be fixed with "xattr -cr myapp.app". After this the program runs normally.