Ignore Firecracker main branch's test failures

Firecracker is making some breaking changes before reaching 1.0.
Due to that, it is hard to make the SDK work with released versions and
main branch.

This commit makes Firecracker main branch's test failures "soft fail",
meaning, tests are still run against the branch, but the failures
wouldn't impact the overall test result.

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

Author: Kazuyoshi Kato

.buildkite/pipeline.yml

@@ -127,6 +127,10 @@ steps:
       queue: "${BUILDKITE_AGENT_META_DATA_QUEUE:-default}"
       distro: "${BUILDKITE_AGENT_META_DATA_DISTRO}"
       hostname: "${BUILDKITE_AGENT_META_DATA_HOSTNAME}"
+    # Firecracker's main branch wouldn't work with Go SDK currently due to ht_enabled change.
+    # https://github.com/firecracker-microvm/firecracker/pull/2876
+    soft_fail:
+      - exit_status: 2
 
   - label: 'go mod tidy'
     commands: