Remove more dead relocation handling code (#3924)

Forgotten from #3905 I now realized.

crates/cranelift/src/obj.rs

@@ -14,9 +14,8 @@
 //! names have format "_trampoline_N", where N is `SignatureIndex`.
 
 use crate::debug::{DwarfSection, DwarfSectionRelocTarget};
-use crate::{CompiledFunction, Relocation, RelocationTarget};
+use crate::{CompiledFunction, RelocationTarget};
 use anyhow::Result;
-use cranelift_codegen::binemit::Reloc;
 use cranelift_codegen::isa::{
     unwind::{systemv, UnwindInfo},
     TargetIsa,
@@ -34,7 +33,6 @@ use object::{
 };
 use std::collections::HashMap;
 use std::convert::TryFrom;
-use std::mem;
 use std::ops::Range;
 use wasmtime_environ::obj;
 use wasmtime_environ::{
@@ -105,12 +103,6 @@ pub struct ObjectBuilder<'a> {
     /// `object`-crate identifier for the text section.
     text_section: SectionId,
 
-    /// Relocations to be added once we've got all function symbols available to
-    /// us. The first entry is the relocation that we're applying, relative
-    /// within a function, and the second entry here is the offset of the
-    /// function that contains this relocation.
-    relocations: Vec<(&'a Relocation, u64)>,
-
     /// In-progress text section that we're using cranelift's `MachBuffer` to
     /// build to resolve relocations (calls) between functions.
     pub text: Box<dyn TextSectionBuilder>,
@@ -171,7 +163,6 @@ impl<'a> ObjectBuilder<'a> {
             windows_unwind_info: Vec::new(),
             systemv_unwind_info_id: None,
             systemv_unwind_info: Vec::new(),
-            relocations: Vec::new(),
             text: isa
                 .text_section_builder((module.functions.len() - module.num_imported_funcs) as u32),
             added_unwind_info: false,
@@ -374,35 +365,6 @@ impl<'a> ObjectBuilder<'a> {
     }
 
     pub fn finish(&mut self) -> Result<()> {
-        // Now that all function symbols are available register all final
-        // relocations between functions.
-        //
-        // FIXME(#3009) once the old backend is removed this loop should be
-        // deleted since there won't be any relocations here.
-        for (r, off) in mem::take(&mut self.relocations) {
-            let symbol = match r.reloc_target {
-                RelocationTarget::UserFunc(index) => self.func_symbols[index],
-                _ => unreachable!("should be handled in `append_func`"),
-            };
-            let (kind, encoding, size) = match r.reloc {
-                Reloc::X86CallPCRel4 => {
-                    (RelocationKind::Relative, RelocationEncoding::X86Branch, 32)
-                }
-                other => unimplemented!("Unimplemented relocation {:?}", other),
-            };
-            self.obj.add_relocation(
-                self.text_section,
-                ObjectRelocation {
-                    offset: off + u64::from(r.offset),
-                    size,
-                    kind,
-                    encoding,
-                    symbol,
-                    addend: r.addend,
-                },
-            )?;
-        }
-
         // Finish up the text section now that we're done adding functions.
         let text = self.text.finish();
         self.obj