at least this solves the missing include statement, so lets go on.
You should always end your paths with / for MicroStation usage, but it should be OK as you currently defined it. Doubled quotes in the MKI might be ignored, missing quotes will lead to errors. Therefore no problem in the asserttoolset.mki.
For me it looks like the linker is not starting and therefore no dll is created. You should show us your mke file (attach it) completely, as there might be options set, that prevent you from successfully linking the (as it seems) successfully compiled object files.