Currently, introspection is not well-supported for ARM64 Windows builds as:
* There is no official Python release for ARM64 Windows, but it is currently
possible to build it with sufficient support for G-I, however...
* The tooling in Python still needs to be updated to enable ARM64 Windows
builds for use with g-ir-scanner and friends, and...
* Introspection builds must be done on an ARM64 system, since we are running a
dumper binary to generate the .gir files
This will attempt to prepare things for building GTK's introspection files on
Windows ARM64, but will require a custom installation of Python as noted above,
for the time being
