More recent versions of Poetry introduced the `package-mode` key to
configure whether the project should be used for dependency management
only, but this is incompatible with the earlier versions of Poetry that
we still support.
Instead, we rely on installing with the `--no-root` flag, which behaves
similarly. Installing without passing the `--no-root` flag is
deprecated, and in recent versions of Poetry has become a hard error.
This change ensures that the build system always installs dependencies
with the required flag.
Change-Id: Ic1543511314dcd20c00b73fd9e8cfae3dd034a41
Signed-off-by: Chris Kay <chris.kay@arm.com>
c25405d613