[erts] Fix harmless configure bug

Author: rickard-green

erts/configure

@@ -16726,7 +16726,7 @@ fi
 if test "$ac_cv_func_strerrorname_np" != "yes"
 then :
 
-         if test $builtin_errno_id = no
+         if test "$builtin_errno_id" = "no"
 then :
   as_fn_error $? "No alternative to builtin erl_errno_id() found" "$LINENO" 5
 fi

erts/configure.ac

@@ -1296,7 +1296,7 @@ AC_CHECK_FUNCS([strerrorname_np])
 
 AS_IF([test "$ac_cv_func_strerrorname_np" != "yes"],
       [
-         AS_IF([test $builtin_errno_id = no],
+         AS_IF([test "$builtin_errno_id" = "no"],
                [AC_MSG_ERROR([No alternative to builtin erl_errno_id() found])])
       ])