IntelliJ generated sources content root and file watcher

This automatically refreshes the generated source files, and the
generated sources folder now has a nice icon.

Potential conflict if anyone uses IntelliJ without the container
(which I'm not aware of).

Test Plan: Modified protobuf file, generated sources were automatically refreshed.

X-Origin-Diff: phab/D234
GitOrigin-RevId: 5f5eb7f2cf541c7dd143564dcad4885476b4bfb0
diff --git a/scripts/create_container.sh b/scripts/create_container.sh
index 0a137bd..449bdb1 100755
--- a/scripts/create_container.sh
+++ b/scripts/create_container.sh
@@ -20,8 +20,10 @@
 
 # Set up SELinux contexts to prevent the container from writing to
 # files that would allow for easy breakouts via tools ran on the host.
-chcon -R system_u:object_r:container_file_t:s0 .
-chcon -R unconfined_u:object_r:user_home_t:s0 \
+chcon -Rh system_u:object_r:container_file_t:s0 .
+
+# Ignore errors - these might already be masked, like when synchronizing the source.
+! chcon -Rh unconfined_u:object_r:user_home_t:s0 \
   .arcconfig .idea .git
 
 # Keep this in sync with ci.sh: