Add macOS 11 Big Sur target to platform_configs. First phase is to cross-compile x86 target with macOS.
The macOS on ARM CI work here: QTQAINFRA-4012
Qt on macOS Big Sur (macOS 11 / 10.16)
Add macOS 11 (Big Sur) into the CI
Qt 6.2 hosts - macOS on ARM64 (moA)
Add macOS on ARM64 (moA) into the CI