fix: catch file not found error when finding location snippet (#1673)

Author: anmonteiro

jscomp/core/ast_io.cppo.ml

@@ -123,6 +123,7 @@ let set_input_lexbuf () =
   in
   begin match set_input_lexbuf !Location.input_name with
   | (_ : Lexing.lexbuf) -> ()
+  | exception Unix.Unix_error (Unix.ENOENT, _, _)
   | exception Sys_error _ -> ()
   end
 

test/blackbox-tests/ppx-location-snippet.t

@@ -18,14 +18,8 @@ Test that the location snippet appears in a ppx-processed compilation error
 
   $ export DUNE_SANDBOX=symlink
   $ dune build @melange
-  File "dune", lines 1-4, characters 0-81:
-  1 | (melange.emit
-  2 |  (target out)
-  3 |  (emit_stdlib false)
-  4 |  (preprocess (pps melange.ppx)))
-  melc: internal error, uncaught exception:
-        Unix.Unix_error(Unix.ENOENT, "open", "foo.ml")
-        
+  File "foo.ml", line 1, characters 7-11:
+  Error: Unbound type constructor nope
   [1]
 
   $ export DUNE_SANDBOX=none