Modifying Makefile in Samples kicks off generation of dry-run... After that, sample then cannot be built or run

Modifying the Makefile in the matrixMul sample causes vscode to kickoff some sort of “dry-run” thing at the next build.
It than chews up a bunch of CPU time and never seems to finish. Once this happens the project appears to be permanently broken. No further builds or runs are possible.

Running make at the command line seems to work fine.