Enhance the base/rom extension to generate the symbol file of the rom built.
The symbol file is placed in epoc32/rom/<baseport_name>, along with the rom log and final oby file.
EXPORTS
_Z9Function3v @ 1 NONAME ; Function3()
_Z9Function4v @ 2 NONAME ; Function4()
_Z11GetDll3Datav @ 3 NONAME ; GetDll3Data()
_Z11SetDll3Datai @ 4 NONAME ; SetDll3Data(int)