Remove root-owned files

Some of the SDK's tests are running as root and create root-owned files.
These files cannot be deleted by BuildKite's agent since the agent is
running as its own user.

This change removes all root-owned files before checking out a Git
repository and finishing each build job.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

Author: Kazuyoshi Kato

.buildkite/hooks/pre-checkout

@@ -0,0 +1,4 @@
+#! /bin/sh
+set -euo pipefail
+
+find . -user root -print0 | xargs -0 sudo rm -rf '{}'

.buildkite/hooks/pre-exit

@@ -1,3 +1,4 @@
 #!/bin/bash
+set -euo pipefail
 
-sudo rm -rf testdata/logs
+find . -user root -print0 | xargs -0 sudo rm -rf '{}'