Add email alerts for nightly pipelines (vllm-project#1095)

Signed-off-by: Pysith Vanuptikul <piv@google.com>

Author: pv97

.buildkite/main.yml

@@ -3,7 +3,7 @@ x-run-condition: &run-on-nightly-or-tag
 
 notify:
   - email: "ullm-oncall@rotations.google.com"
-    if: build.state == "failed" && build.branch == "main"
+    if: build.state == "failed"
 
 steps:
    - label: "Upload Tests for Models & Features"

.buildkite/nightly_releases.yml

@@ -1,3 +1,7 @@
+notify:
+  - email: "ullm-oncall@rotations.google.com"
+    if: build.state == "failed"
+
 steps:
   - label: "Publish vllm/vllm-tpu nightly image"
     if: build.env("NIGHTLY") == "1"