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
_ZN11UnicodeConv19ConvertFromUnicodeLER5TDes8RK7TDesC16 @ 1 NONAME
_ZN11UnicodeConv17ConvertToUnicodeLER6TDes16RK6TDesC8 @ 2 NONAME
_ZN11UnicodeConv25IsLegalShortNameCharacterEj @ 3 NONAME
_ZN11UnicodeConv19ConvertFromUnicodeLER5TDes8RK7TDesC16i @ 4 NONAME
_ZN11UnicodeConv17ConvertToUnicodeLER6TDes16RK6TDesC8i @ 5 NONAME