Rewrite LLVM's archive writer in Rust

This allows it to be used by other codegen backends

Cargo.lock

@@ -92,6 +92,15 @@ version = "1.0.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "98161a4e3e2184da77bb14f02184cdd111e83bbbcc9979dfee3c44b9a85f5602"
 
+[[package]]
+name = "ar_archive_writer"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "276881980556fdadeb88aa1ffc667e4d2e8fe72531dfabcb7a82bb3c9ea9ba31"
+dependencies = [
+ "object",
+]
+
 [[package]]
 name = "array_tool"
 version = "1.0.3"
@@ -3413,6 +3422,7 @@ dependencies = [
 name = "rustc_codegen_ssa"
 version = "0.0.0"
 dependencies = [
+ "ar_archive_writer",
  "bitflags",
  "cc",
  "itertools",