doc-rst: Delete output of failed dot-SVG conversion

As we use redirection to create the SVG file, even a failed conversion
will create the file and 'make' will consider it up-to-date if the
build is retried.  We should delete it in case of failure.

Fixes: ec868e4ee2 ("docs-rst: media: build SVG from graphviz files")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Ben Hutchings 2017-01-31 00:18:44 +00:00 • committed by Jonathan Corbet
commit 04b7091172