Add copy_files stanzas to affeq-test dune

Author: kadameit

tests/unit/dune

@@ -17,4 +17,10 @@
   (dev
     (flags (:standard -warn-error -A -w -unused-var-strict)) ; https://dune.readthedocs.io/en/stable/faq.html#how-to-make-warnings-non-fatal
   )
-)
+)
+
+; Workaround for alternative dependencies with unqualified subdirs.
+; See: https://github.com/ocaml/dune/issues/4383#issuecomment-805107435.
+; TODO: Remove workaround with dune 3.0, where this should get fixed.
+; A dune file with "include_subdirs no" is located in cdomains/affineEqualityDomain to avoid a dependency cycle
+(copy_files# cdomains/affineEqualityDomain/sparseImplementation/*.ml)