Following the instructions inside the ebuild to setup ifc, results in the following error checking for main in -lieee... yes checking for g77... no checking for f2c... no configure: error: Unable to configure: no Fortran compiler found !!! ERROR: app-sci/scilab-3.0 failed. !!! Function econf, Line 441, Exitcode 1 !!! econf failed !!! If you need support, post the topmost build error, NOT this status message.
If configure fails to find "ifc", there is a problem with your IFC installation. SciLab builds with IFC without problem here. I suggest you reinstall "dev-lang/ifc".