Fix: The alloc crate uses the Rust 2021 edition now

The alloc library was switched to the 2021 edition in <rust-lang/rust#92068>. However, it did not use any features of the new edition until PR <rust-lang/rust#98103>, which relies on the newer closure capture mechanism. This commit fixes the build on the latest nightlies, which include that PR.

Fixes #104

Author: phil-opp

src/sysroot.rs

@@ -177,7 +177,7 @@ fn build_liballoc(
 authors = ["The Rust Project Developers"]
 name = "alloc"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies.compiler_builtins]
 version = "0.1.0"