Kokoro: Allow 'Fixes:' in bug check

This adds to 'Bug:', 'Issue:' and 'Regres:' as accepted CL grep checks.

Fixes: b/143093187
Change-Id: Iae44d8e8e49f7534bb940ec977edb4afcddc308e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/37449
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
diff --git a/tests/kokoro/gcp_ubuntu/continuous.sh b/tests/kokoro/gcp_ubuntu/continuous.sh
index 2528f3c..ffb48b8 100644
--- a/tests/kokoro/gcp_ubuntu/continuous.sh
+++ b/tests/kokoro/gcp_ubuntu/continuous.sh
@@ -3,7 +3,7 @@
 cd git/SwiftShader
 
 # Validate commit message
-git log -1 --pretty=%B | grep -E '^Bug:|^Issue:|^Regres:'
+git log -1 --pretty=%B | grep -E '^Bug:|^Issue:|^Fixes:|^Regres:'
 
 if [ $? -ne 0 ]
 then