To generate Windows ARM64 builds set the CEF_ENABLE_ARM64=1 environment
variable and pass the "--arm64-build --build-target=cefsimple" command-line
arguments to automate-git.py. We can't build cefclient.exe for ARM64 due to
missing OpenGL library support so build cefsimple.exe instead.
Requires Xcode 12.2 and the MacOS 11.0 SDK. To generate ARM64 builds set
the CEF_ENABLE_ARM64=1 environment variable and replace all usage of
--x64-build with --arm64-build in script command-line arguments.
