git ignore: avoid ccaches stored for Chronos (#14279)

We use the `ccaches` folder to store ccaches when testing
`replay_build.sh`. We don't want these committed though.

Signed-off-by: David Korczynski <david@adalogics.com>

Author: DavidKorczynski

.gitignore

@@ -12,3 +12,6 @@ infra/base-images/base-builder/indexer/fuzzing_engine.a
 # IntelliJ IDEA
 /.idea
 **/*.iml
+
+# Chronos
+ccaches/