Include checkbuild in list of required target

We should never remove checkbuild right now when it is specified.

Change-Id: I71fe5417f4f863e3b499a0f25534a374050bd064
Test: presubmit
Bug: 378704055
diff --git a/ci/build_test_suites.py b/ci/build_test_suites.py
index 88630ba..addad15 100644
--- a/ci/build_test_suites.py
+++ b/ci/build_test_suites.py
@@ -35,7 +35,7 @@
 LOG_PATH = 'logs/build_test_suites.log'
 # Currently, this prevents the removal of those tags when they exist. In the future we likely
 # want the script to supply 'dist directly
-REQUIRED_BUILD_TARGETS = frozenset(['dist', 'droid'])
+REQUIRED_BUILD_TARGETS = frozenset(['dist', 'droid', 'checkbuild'])
 
 
 class Error(Exception):