Fix aarch64-unknown-linux-gnu_ilp32 target

This was broken because the synthetic object files produced by rustc
were for 64-bit AArch64, which caused link failures when combined with
32-bit ILP32 object files.

This PR updates the object crate to 0.30.1 which adds support for
generating ILP32 AArch64 object files.

compiler/rustc_codegen_ssa/Cargo.toml

@@ -15,7 +15,7 @@ tracing = "0.1"
 libc = "0.2.50"
 jobserver = "0.1.22"
 tempfile = "3.2"
-thorin-dwp = "0.3"
+thorin-dwp = "0.4"
 pathdiff = "0.2.0"
 serde_json = "1.0.59"
 snap = "1"
@@ -43,6 +43,6 @@ rustc_session = { path = "../rustc_session" }
 rustc_const_eval = { path = "../rustc_const_eval" }
 
 [dependencies.object]
-version = "0.29.0"
+version = "0.30.1"
 default-features = false
 features = ["read_core", "elf", "macho", "pe", "unaligned", "archive", "write"]

compiler/rustc_codegen_ssa/src/back/metadata.rs

@@ -100,7 +100,13 @@ pub(crate) fn create_object_file(sess: &Session) -> Option<write::Object<'static
     };
     let architecture = match &sess.target.arch[..] {
         "arm" => Architecture::Arm,
-        "aarch64" => Architecture::Aarch64,
+        "aarch64" => {
+            if sess.target.pointer_width == 32 {
+                Architecture::Aarch64_Ilp32
+            } else {
+                Architecture::Aarch64
+            }
+        }
         "x86" => Architecture::I386,
         "s390x" => Architecture::S390x,
         "mips" => Architecture::Mips,