try adding more things to the PATH on Windows, maybe it helps

src/bootstrap/src/core/builder.rs

@@ -1272,8 +1272,10 @@ impl<'a> Builder<'a> {
         cmd.env("MIRI", &miri);
         cmd.env("CARGO", &self.initial_cargo);
         // Need to add the run_compiler libs. Not entirely sure why that has to be one stage up from
-        // what Miri was built for.
-        self.add_rustc_lib_path(run_compiler, &mut cmd);
+        // what Miri was built for. Also, we can't use `add_rustc_lib_path` as that's a NOP on
+        // Windows but without our help Windows can't find the libs here, so we inline what it does
+        // instead.
+        add_dylib_path(self.rustc_lib_paths(run_compiler), &mut cmd);
         cmd
     }