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
	ExportedData @ 1 NONAME ; TInt32 ExportedData
	CheckExportedDataAddress__FPv @ 2 NONAME ; void CheckExportedDataAddress(void* aDataAddr)