buildman: Create parent directories as necessary

When creating build directories also create parents as necessary. This
fixes a failure when building a hierarchical branch (i.e. foo/bar).

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Tom Rini <trini@ti.com>
2 files changed