I found:
/usr/local/lib/libiconv.sl.4
/usr/local/lib/libiconv.sl.4.0
/usr/local/lib/libiconv.sl
/usr/local/lib/libiconv.la
/usr/local/share/doc/libiconv
so I think is installed
However, yes, I'm trying to build gdb for debugging 64 bit code....but how can I pass the ELF option to gcc? And I don't understand how can elfdump help me...