
Setting Spack's `$prefix` to `$DESTDIR` and not to `$PREFIX` install the package in `$prefix/usr/local` and not in `$prefix`, thus when it is loaded the executable `direnv` in not "seen" by the environment.
Setting Spack's `$prefix` to `$DESTDIR` and not to `$PREFIX` install the package in `$prefix/usr/local` and not in `$prefix`, thus when it is loaded the executable `direnv` in not "seen" by the environment.