Stop using a custom Cargo.toml and Cargo.lock for the standard library

The rust-src component now ships a working copy of both.

build_system/prepare.rs

@@ -22,36 +22,6 @@ pub(crate) fn prepare_stdlib(dirs: &Dirs, rustc: &Path) {
     assert!(sysroot_src_orig.exists());
 
     apply_patches(dirs, "stdlib", &sysroot_src_orig, &STDLIB_SRC.to_path(dirs));
-
-    std::fs::write(
-        STDLIB_SRC.to_path(dirs).join("Cargo.toml"),
-        r#"
-[workspace]
-resolver = "1"
-members = ["./library/sysroot"]
-
-[patch.crates-io]
-rustc-std-workspace-core = { path = "./library/rustc-std-workspace-core" }
-rustc-std-workspace-alloc = { path = "./library/rustc-std-workspace-alloc" }
-rustc-std-workspace-std = { path = "./library/rustc-std-workspace-std" }
-
-# Mandatory for correctly compiling compiler-builtins
-[profile.dev.package.compiler_builtins]
-debug-assertions = false
-overflow-checks = false
-codegen-units = 10000
-
-[profile.release.package.compiler_builtins]
-debug-assertions = false
-overflow-checks = false
-codegen-units = 10000
-"#,
-    )
-    .unwrap();
-
-    let source_lockfile = RelPath::PATCHES.to_path(dirs).join("stdlib-lock.toml");
-    let target_lockfile = STDLIB_SRC.to_path(dirs).join("Cargo.lock");
-    fs::copy(source_lockfile, target_lockfile).unwrap();
 }
 
 pub(crate) struct GitRepo {