Multiple defintion error, Linker error
You forgot the -c flag to your first command. That means you have first compiled your program into a full elf file. Then you try to link that elf file with the standard startup libraries again (it already contains them) into another new elf file.

And so you get duplicate entries in it.

Add -c to your first command, which means "compile only, don't link" to create object files not an elf file.