treewide: explicity load built-in rules

In Bazel 9 all autoloaded rules will be disabled. This prepares us for
that.

Change-Id: Ibaa4fa2e6b7095922a5699d2d5f3ae6c2cba3552
Reviewed-on: https://review.monogon.dev/c/monogon/+/3939
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/build/toolchain/musl-host-gcc/BUILD.bazel b/build/toolchain/musl-host-gcc/BUILD.bazel
index 2d1524f..39a0eb4 100644
--- a/build/toolchain/musl-host-gcc/BUILD.bazel
+++ b/build/toolchain/musl-host-gcc/BUILD.bazel
@@ -1,3 +1,4 @@
+load("@rules_cc//cc:defs.bzl", "cc_toolchain")
 load("//build/toolchain:cc_toolchain_config.bzl", "host_cc_toolchain_config")
 
 # This file defines //build/toolchain/musl-host-gcc:musl_host_toolchain.