Revert "[PATCH] Remove --root on dune calls - does not work on Windows MinGW"

This reverts commit e684402c.

src/patch/Makefile

 mlpatch : lexer.mll parser.mly patch.ml mlpatch.ml
-	dune build
+	dune build --root $(CURDIR)
 
 clean :
-	dune clean
+	dune clean --root $(CURDIR)