net-p2p/monero-cli: Fix compilation on i386

/usr/src/contrib/llvm/tools/lld/ELF/Driver.cpp:126 contains
"elf_i386" as a recognized name, but for some reason monero fails
to link on the i386 build cluster with an error:

/usr/bin/ld: unrecognised emulation mode: elf_i386
Supported emulations: elf_i386_fbsd

Thus, change "elf_i386" to "elf_i386_fbsd".