emake displays this error when there is a problem processing a rename operation encountered during the build.
When emake executes a build, it executes jobs in a virtualized filesystem context, rather than directly against the real filesystem. This gives emake the flexibility to revert jobs if necessary due to conflicts, and also eliminates the risk that simultaneously running jobs will interfere with each other. Only after a job has been verified to be free of conflicts will emake apply the filesystem operations recorded in the virtualized filesystem to the real filesystem. Error EC1124 indicates that an error was encountered when apply a rename operation to the real filesystem. The source and target of the rename operation are given in the error message.
Because emake is interacting with an external entity — here, the filesystem on the host from which emake was invoked — the list of possible causes for this error is virtually limitless: out of disk space on the emake client; a failed network connection to the agent; hardware failure of some sort; etc. Read the OS error message to determine the specific cause of the failure.
One possible cause for this error is that another process has modified the build output area while emake is running. This can lead to unpredictable results and should be avoided if possible.
The fix depends on the specific cause of the error.