Drush vagrant-build fails with error "egrep" is not recognized

First I had to switch from Drush 8 to Drush 7. This module does not work with Drush 8 on my Windows machine. Then:
Using Drush7:

When executing
drush vagrant-build
it fails with the errors:

'egrep' is not recognized as an internal or external command, operable program or batch file.

symlink(): cannot create symlink, error code (1314)
vagrant.blueprints.inc:92

..etc