Use large-model addressing for calls when in non-PIC mode.

The main use for non-PIC code at present is JIT code, and JIT code can
live anywhere in memory and reference other symbols defined anywhere in
memory, so it needs to use the "large" code model.

func_addr and globalsym_addr instructions were already using `movabs`
to support arbitrary 64-bit addresses, so this just makes calls be
legalized to support arbitrary 64-bit addresses also.

cranelift/filetests/isa/intel/legalize-libcall.cton

@@ -2,6 +2,7 @@ test legalizer
 
 ; Pre-SSE 4.1, we need to use runtime library calls for floating point rounding operations.
 set is_64bit
+set is_pic
 isa intel
 
 function %floor(f32) -> f32 {