consider cfg as private

valuable/build.rs

@@ -4,19 +4,9 @@ use std::env;
 
 include!("no_atomic_cas.rs");
 
-// The rustc-cfg listed below are considered public API, but it is *unstable*
-// and outside of the normal semver guarantees:
-//
-// - `valuable_no_atomic_cas`
-//      Assume the target does *not* support atomic CAS operations.
-//      This is usually detected automatically by the build script, but you may
-//      need to enable it manually when building for custom targets or using
-//      non-cargo build systems that don't run the build script.
-//
-// With the exceptions mentioned above, the rustc-cfg strings below are
-// *not* public API. Please let us know by opening a GitHub issue if your build
-// environment requires some way to enable these cfgs other than by executing
-// our build script.
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
 fn main() {
     let target = match env::var("TARGET") {
         Ok(target) => target,