Bazel: fix build with Bazel 0.25.

Change-Id: I040173bd2b732671fb37bd8df4641f28f73f84b6
Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Reviewed-on: https://nginx-review.googlesource.com/c/nginx/+/3640
Reviewed-by: Daniel Berkovitch <dbrk@google.com>
diff --git a/BUILD b/BUILD
index 971c1b0..992b31c 100644
--- a/BUILD
+++ b/BUILD
@@ -158,6 +158,7 @@
           " --without-http_upstream_zone_module" +
           " 2>&1 >$(@D)/bazel-objs/autoconf.log",
     toolchains = [
+        "@bazel_tools//tools/cpp:cc_flags",
         "@bazel_tools//tools/cpp:current_cc_toolchain",
     ],
     visibility = [