The message comes from Go. The docker branch I cited in the other thread resolved that by ensuring that meta-virtualization uses a Go version that we patched to resolve that MMX dependency. If you build that branch, you will get a "working" version (with all the inherent limitations).

If you build your own version: Meanwhile things moved on, meta-virtualization as well as Go. A lot of work would be needed, including updating Go patches (see also https://github.com/siemens/meta-iot2000/issues/96).