Find libc symbols in symbol discovery

[ExPixel]

At the moment if you run cargo disasm copy_nonoverlapping, this is the output:

core::intrinsics::copy_nonoverlapping:
  cc6e0    sub   rsp, 0x28                      
  cc6e4    mov   qword ptr [rsp + 0x10], rdi    
  cc6e9    mov   qword ptr [rsp + 0x18], rsi    
  cc6ee    mov   qword ptr [rsp + 0x20], rdx  
  cc6f3    shl   rdx, 4                         
  cc6f7    mov   qword ptr [rsp + 8], rdi       
  cc6fc    mov   rdi, rsi                       
  cc6ff    mov   rsi, qword ptr [rsp + 8]       
  cc704    call  0xba150                        ; Not symbolicated
  cc709    add   rsp, 0x28                      
  cc70d    ret

For some reason the symbol for memcpy isn't being found using the current symbol discovery methods. I think it might
have something to do with this:

cargo-disasm/src/disasm/binary.rs

Lines 318 to 321 in 57161ab

	// FIXME handle symbols with a size of 0 (usually external symbols).
	if sym.st_size == 0 {
	continue;
	}

But I'm not sure.