Avoid downgrading to Stable despite RUSTC_BOOTSTRAP

error[E0658]: use of unstable library feature 'portable_simd'
  --> cargo-crates/vek-0.17.0/src/vec.rs:18:5
   |
18 | use std::simd::SimdElement;
   |     ^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #86656 <https://github.com/rust-lang/rust/issues/86656> for more information
   = help: add `#![feature(portable_simd)]` to the crate attributes to enable
   = note: this compiler was built on 2024-04-29; consider upgrading it if it is out of date

--- cargo-crates/vek-0.17.1/build.rs.orig	1970-01-01 00:00:00 UTC
+++ cargo-crates/vek-0.17.1/build.rs
@@ -4,23 +4,6 @@ fn main() {
 fn main() {
     assert!(version().unwrap().major >= 1);
 
-    println!("cargo:rustc-check-cfg=cfg(stable)");
-    println!("cargo:rustc-check-cfg=cfg(beta)");
-    println!("cargo:rustc-check-cfg=cfg(nightly)");
-    println!("cargo:rustc-check-cfg=cfg(dev)");
-    match version_meta().unwrap().channel {
-        Channel::Stable => {
-            println!("cargo:rustc-cfg=stable");
-        }
-        Channel::Beta => {
-            println!("cargo:rustc-cfg=beta");
-        }
-        Channel::Nightly => {
-            println!("cargo:rustc-cfg=nightly");
-        }
-        Channel::Dev => {
-            println!("cargo:rustc-cfg=dev");
-        }
-    }
+    println!("cargo:rustc-cfg=nightly");
 }