expose -Zpolonius flag

Author: qmx

src/librustc/session/config.rs

@@ -1296,6 +1296,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
                        "dump facts from NLL analysis into side files"),
     disable_nll_user_type_assert: bool = (false, parse_bool, [UNTRACKED],
         "disable user provided type assertion in NLL"),
+    polonius: bool = (false, parse_bool, [UNTRACKED],
+        "enable polonius-based borrow-checker"),
     codegen_time_graph: bool = (false, parse_bool, [UNTRACKED],
         "generate a graphical HTML report of time spent in codegen and LLVM"),
     thinlto: Option<bool> = (None, parse_opt_bool, [TRACKED],