Why not to use libexecdir?
Because this directory does not exist on some distros or paths
between distros varies. There are several reasons why a well
known path is prefered, for example when generating a kernel
command line:
init=${ostree}/usr/lib/ostree-boot/ostree-prepare-root
In addition this saves us some typing in a console when wanting
to access the "ostree" cmd line.
Closes: #449
Approved by: cgwalters
Gatis Paeglis
Giuseppe Scrivano
Daniel Narvaez