Rollup merge of #144503 - bjorn3:lto_refactors3, r=petrochenkov

Various refactors to the codegen coordinator code (part 3)

Continuing from rust-lang/rust#144062 this removes an option without any known users, uses the object crate in favor of LLVM for getting the LTO bitcode and improves the coordinator channel handling.

Author: matthiaskrgr

src/back/write.rs

@@ -4,7 +4,6 @@ use gccjit::{Context, OutputKind};
 use rustc_codegen_ssa::back::link::ensure_removed;
 use rustc_codegen_ssa::back::write::{BitcodeSection, CodegenContext, EmitObj, ModuleConfig};
 use rustc_codegen_ssa::{CompiledModule, ModuleCodegen};
-use rustc_errors::DiagCtxtHandle;
 use rustc_fs_util::link_or_copy;
 use rustc_session::config::OutputType;
 use rustc_span::fatal_error::FatalError;
@@ -258,14 +257,6 @@ pub(crate) fn codegen(
     ))
 }
 
-pub(crate) fn link(
-    _cgcx: &CodegenContext<GccCodegenBackend>,
-    _dcx: DiagCtxtHandle<'_>,
-    mut _modules: Vec<ModuleCodegen<GccContext>>,
-) -> Result<ModuleCodegen<GccContext>, FatalError> {
-    unimplemented!();
-}
-
 pub(crate) fn save_temp_bitcode(
     cgcx: &CodegenContext<GccCodegenBackend>,
     _module: &ModuleCodegen<GccContext>,

src/lib.rs

@@ -426,14 +426,6 @@ impl WriteBackendMethods for GccCodegenBackend {
     fn serialize_module(_module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer) {
         unimplemented!();
     }
-
-    fn run_link(
-        cgcx: &CodegenContext<Self>,
-        dcx: DiagCtxtHandle<'_>,
-        modules: Vec<ModuleCodegen<Self::Module>>,
-    ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
-        back::write::link(cgcx, dcx, modules)
-    }
 }
 
 /// This is the entrypoint for a hot plugged rustc_codegen_gccjit