According to gcc-9.1.0/NEWS Intel i860 was an architecture declared
obsolete in GCC 4.0 (and previously in GCC 3.1).
So you could check the configuration files are there in 3.4.6
(2006-03-10) or in 4.0.4 (2007-01-31).
The binutils/gas/i860 configuration files were removed in 2018-04-11, so
binutils 2.30 (2018-01-28) may still be able to build cross binutils
assemblers and linkers for the architecture. I don't have an unpacked
gdb lying around to check.
The announce mailing list archives
may be worth checking if
the config isn't in gdb.