There is a special rule in make(1) to denote that we don't care about
the result of a command. Additionally, we can also instruct rm(1) not
to complain when it didn't find a file/directory to remove.
As a final touch, there is no point of having 2 shell executions to
remove 2 or more files. We can compress these 2 recipes into a single
one.
Reference:
https://www.gnu.org/software/make/manual/html_node/Errors.html
Christos Kontas
Kevin Schoon