third_party/linux: use toolchain-bundle for linux kernel build

This contains lots of workarounds and should be migrated to a native
bazel integration.

Change-Id: Ib0a52daf3879df4d5369541475c42fa506a54328
Reviewed-on: https://review.monogon.dev/c/monogon/+/4101
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/osbase/test/ktest/BUILD.bazel b/osbase/test/ktest/BUILD.bazel
index 654416e..3d8bb2a 100644
--- a/osbase/test/ktest/BUILD.bazel
+++ b/osbase/test/ktest/BUILD.bazel
@@ -41,6 +41,7 @@
     name = "linux-testing",
     image_format = "vmlinux",
     kernel_config = ":testing-config",
+    kernel_src = "@linux//:all",
     # This image is directly used by the ktest macro, thus it needs a pretty
     # wide visibility.
     visibility = [