Explicitly enable workspace for some tasks (#540)

diff --git a/.bazelci/presubmit.yml b/.bazelci/presubmit.yml
index 176e998..b133407 100644
--- a/.bazelci/presubmit.yml
+++ b/.bazelci/presubmit.yml
@@ -72,9 +72,11 @@
     build_flags:
       <<: *reusable_build_flags
       ? "--noenable_bzlmod"
+      ? "--enable_workspace"
     test_flags:
       <<: *reusable_test_flags
       ? "--noenable_bzlmod"
+      ? "--enable_workspace"
     build_targets:
       <<: *reusable_targets
       # rules_pkg fails with --noenable_bzlmod