[OCaml] Clear cross-target test deps when building out-of-tree Clear cross-target test dependencies when using LLVM_OCAML_OUT_OF_TREE, in order to make it possible to run check-llvm-bindings-ocaml without rebuilding the whole LLVM. Differential Revision: https://reviews.llvm.org/D26580 llvm-svn: 286720 GitOrigin-RevId: a583be4e52d9f7d0fd36e1d44836d8297cedda2a