Not rebuilding existing files

I've created a custom action that creates import libraries
from dlls.

It looks like this:

:action implib lib dll
     :sys implib /noi /system $target $source

and the route

:route dll lib
     implib

I call it by using

:do implib {target = $lib} $dll

Now, if I execute the recipe again, the import libraries are rebuilt
unnecessarily. It seems like I'm unable to find out how to not rebuild
if they already exists. Is there an easy way to add this to the code
above? I don't think this  stuff warrants an inclusion into A-A-P and
thus I want to make as small a recipe for it as possible.

Lars Ivar Igesund


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