--ignore-missing / --if-exists flag for building optional targets

[guybedford]

It might useful to have a chomp --ignore-missing targetA targetB which ignores targets not defined in the Chompfile (say it only defines targetA but not targetB).

Eg when building a monorepo it would avoid failing a test task being interpolated where projects don't define a test task.

--ignore-missing / -m or --if-exists / -e could be possible flags for this.

[guybedford]

Alternatively --if-present.