Robohelp HTML command-line utility overwrites merged files in .hhp file with absolute paths. Any way to prevent this?

I have a Robohelp 11 HTML project which uses merged CHM files. I have a help build script which compiles this project using the RH command-line utility. Whenever this runs, RH overwrites the names of the merged CHM files in the .hhp file to use absolute paths (even if the .hhp file is read-only!). I've searched Adobe forums and this appears to be a RH bug. In my case, it doesn't stop the project performing the merge, but it looks like it causes problems when searching the resultant parent CHM (topics matching the search simply don't show up in child projects), as the search cannot necessarily find the merged files referenced in the .hhp when someone performs the search on a different machine. I notice that if I compile via the RH UI, the .hhp entries are not overwritten. So, a workaround is to do the build manually. However, we'd like to automate our help build. Is there any way to prevent the command-line compiler overwriting the merge file entries in the .hhp?