Add a build status badge

README.md

diff --git a/README.md b/README.md
index 8b5acd4..792dcca 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+[![Build status](https://badge.buildkite.com/a8860e94a7378491ce8f50480e3605b49eb2558cfa851bbf9b.svg)](https://buildkite.com/bazel/kotlin-postsubmit)
+
 [Skydoc documentation](https://bazelbuild.github.io/rules_kotlin)
 
 # Announcements
@@ -22,4 +24,4 @@
   * `resources_strip_prefix`
   * `exports`
 * Persistent worker support.
-* Mixed-Mode compilation (compile Java and Kotlin in one pass).
\ No newline at end of file
+* Mixed-Mode compilation (compile Java and Kotlin in one pass).