tools: --check-cfg has been stabilized

rust-lang/rust#123501

tools/build.sh

@@ -194,12 +194,13 @@ nightly=''
 if [[ "${rustc_version}" == *"nightly"* ]] || [[ "${rustc_version}" == *"dev"* ]]; then
     nightly=1
     rustup ${pre_args[@]+"${pre_args[@]}"} component add rust-src &>/dev/null
-    # The latest syntax of -Z check-cfg requires 1.75.0-nightly.
+    # The latest syntax of cargo -Z check-cfg requires 1.75.0-nightly.
+    # rustc --check-cfg has been stabilized in 1.79.
     # We only check this on the recent nightly to avoid old clippy bugs.
     # shellcheck disable=SC2207
     if [[ "${rustc_minor_version}" -ge 79 ]]; then
         build_scripts=(build.rs)
-        check_cfg='-Z unstable-options --check-cfg=cfg(target_pointer_width,values("128")) --check-cfg=cfg(target_arch,values("xtensa")) --check-cfg=cfg(target_feature,values("x87","lse2","lse128","rcpc3","v8m","partword-atomics","quadword-atomics","fast-serialization"))'
+        check_cfg='--check-cfg=cfg(target_pointer_width,values("128")) --check-cfg=cfg(target_arch,values("xtensa")) --check-cfg=cfg(target_feature,values("x87","lse2","lse128","rcpc3","v8m","partword-atomics","quadword-atomics","fast-serialization"))'
         known_cfgs+=($(grep -E 'cargo:rustc-cfg=' "${build_scripts[@]}" | sed -E 's/^.*cargo:rustc-cfg=//; s/(=\\)?".*$//' | LC_ALL=C sort -u))
         # TODO: handle multi-line target_feature_if
         known_target_feature_values+=($(grep -E 'target_feature_if\("' "${build_scripts[@]}" | sed -E 's/^.*target_feature_if\(//; s/",.*$/"/' | LC_ALL=C sort -u))