Fix buck2 targets command for non-ocamlrep users of the fbcode shim (#79

)

Summary:
Pull Request resolved: #79
X-link: pytorch/executorch#3563
X-link: facebook/folly#2185

Test Plan: CI on the ocamlrep PR passes

Reviewed By: shayne-fletcher

Differential Revision: D57006939

Pulled By: bigfootjon

fbshipit-source-id: bd70508ee634e8089b41f19cbfd471a6a7b9901d

ocaml-setup.sh

@@ -24,7 +24,7 @@ set -u
 
 # Link 'third-party/ocaml/opam'.
 if [ ! -L shim/third-party/ocaml/opam ]; then
-  (cd shim/third-party/ocaml && ln -s "$OPAM_SWITCH_PREFIX" opam)
+  (cd shim/third-party/ocaml && rm -rf opam && ln -s "$OPAM_SWITCH_PREFIX" opam)
 else
     echo "Link 'shim/third-party/ocaml/opam' exists. To overwrite it, first remove it and run $0 again"
 fi

shim/third-party/ocaml/opam/lib/ocaml

@@ -0,0 +1 @@
+# Fake file so that buck2 can run in non-ocamlrep repos