Read-Only Root Filesystem check should check mounted folders and advise to mount appropriate folders

[psantus]

Read-Only Root Filesystem is not a definite obstacle to ECS Exec (event if that's not covered in the officiel Documentation).

Creating bind mounts for the following folders will actually enable the Managed Agent to perform the writes it needs to perform

/managed-agents 
/var/lib/amazon/ssm
/var/log/amazon/ssm

The checker could verify that. Or at least advise to try that.