Update the reason why we need conscrypt and core-icu4j.

So that we don't repeat https://r.android.com/1828052 without running
the relevant tests.

Test: n/a - comment change only
Change-Id: Ibe1ba54d2271069626d80dc4ae9484c55f207bc8
diff --git a/tools/buildbot-build.sh b/tools/buildbot-build.sh
index 8b33bfa..d5fee20 100755
--- a/tools/buildbot-build.sh
+++ b/tools/buildbot-build.sh
@@ -110,7 +110,8 @@
   make_command+=" build-art-target-tests"
   make_command+=" libnetd_client-target toybox sh libtombstoned_client"
   make_command+=" debuggerd su"
-  # vogar requires the class files for conscrypt and ICU.
+  # testrunner in chroot requires the class files for conscrypt and ICU (cf.
+  # https://r.android.com/1828052).
   make_command+=" conscrypt core-icu4j"
   make_command+=" ${ANDROID_PRODUCT_OUT#"${ANDROID_BUILD_TOP}/"}/system/etc/public.libraries.txt"
   # Targets required to generate a linker configuration for device within the