Update dln.c to fix error output from `dln_open()`

`libruby_name` gets trashed by `dlclose(handle)`, so output the
"linked to incompatible ... " error before calling `dlclose(handle)`.

dln.c

@@ -392,6 +392,12 @@ dln_open(const char *file)
                 dln_fatalerror("%s - %s", incompatible, file);
             }
             else {
+                if (libruby_name) {
+                    const size_t len = strlen(libruby_name);
+                    char *const tmp = ALLOCA_N(char, len + 1);
+                    if (tmp) memcpy(tmp, libruby_name, len + 1);
+                    libruby_name = tmp;
+                }
                 dlclose(handle);
                 if (libruby_name) {
                     dln_loaderror("linked to incompatible %s - %s", libruby_name, file);