gtk4-update-icon-cache: Avoid UAC on 32-bit Windows

gtk4-update-icon-cache: Avoid UAC on 32-bit Windows

As the program executable name has 'update' in its filename,
gtk4-update-icon-cache.exe is considered to be an installer program on 32-bit
Windows [1], which will cause the program to fail to run unless it is running
with elevated privileges (i.e. UAC).

Avoid this situation by embedding a manifest file into the final executable
that tells Windows that this is not a program that requires elevation.

Fixes issue #3632.

[1]: https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-vista/cc709628(v=ws.10)?redirectedfrom=MSDN,
     under section "Installer Detection  Technology"