Test macOS Universal binaries

For adding macOS Universal binaries to RTA tests, following steps needs to be done:

Create new label: https://intranet.qt.io/display/QTRD/How+to%3A+add+or+update+configuration+label

Note the differences against macOS-clang-11.0-x64:

install_dirs = clang_64  <-- change
install_dir_host = %(install_dirs_clang_64)s<-- change
package_names = clang_64<-- change

Afaik the universal has 'macos' instead of 'clang_64', you can try with that, if it's not working ask Antti.

Name it macOS-clang-11.0-x64-universal

Add to following jobs:

RTA_smoke_installer_mac

RTA_smoke_creator_mac

RTA_installer_full_mac

RTA_installer_licheck

As a last step new test should be created which installs both binaries to see that they are not interfering each other. It could be done to installer_full test (add if-else so that it will skip Qt6). New label is needed for that: macOS-clang-11.0-x64-multi. Follow instructions above. Now there should be both clang_64 and macos as the package name etc