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
_Z7Export1v @ 1 NONAME ; Export1()
_Z7Export2v @ 2 NONAME ; Export2()
_Z7Export3v @ 3 NONAME ; Export3()
_Z7Export4v @ 4 NONAME ABSENT ; Export4()
_Z7Export5i @ 5 NONAME ABSENT ; Export5(int)
_Z7Export6i @ 6 NONAME ; Export6(int)