Auto merge of #3410 - Urgau:new-check-cfg-syntax, r=JohnTitor

Use new check-cfg syntax in newer nightly

[MCP636 - Simplify and improve explicitness of the check-cfg syntax](rust-lang/compiler-team#636) introduced a new syntax for check-cfg.

This PR adjust the `build.rs` code to use the new syntax on `rustc >= 75`.
The old syntax is still used on older version since on rust-lang/rust we need to be compatible with both for now.

Author: bors

.github/workflows/bors.yml

@@ -333,7 +333,7 @@ jobs:
       - name: Setup Rust toolchain
         run: TOOLCHAIN=nightly sh ./ci/install-rust.sh
       - name: Build with check-cfg
-        run: LIBC_CI=1 LIBC_CHECK_CFG=1 cargo build -Z unstable-options -Z check-cfg=features,names,values,output
+        run: LIBC_CI=1 LIBC_CHECK_CFG=1 cargo build -Z unstable-options -Z check-cfg
 
   # These jobs doesn't actually test anything, but they're only used to tell
   # bors the build completed, as there is no practical way to detect when a

build.rs

@@ -167,11 +167,19 @@ fn main() {
     // https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg
     if libc_check_cfg {
         for cfg in ALLOWED_CFGS {
-            println!("cargo:rustc-check-cfg=values({})", cfg);
+            if rustc_minor_ver >= 75 {
+                println!("cargo:rustc-check-cfg=cfg({})", cfg);
+            } else {
+                println!("cargo:rustc-check-cfg=values({})", cfg);
+            }
         }
         for &(name, values) in CHECK_CFG_EXTRA {
             let values = values.join("\",\"");
-            println!("cargo:rustc-check-cfg=values({},\"{}\")", name, values);
+            if rustc_minor_ver >= 75 {
+                println!("cargo:rustc-check-cfg=cfg({},values(\"{}\"))", name, values);
+            } else {
+                println!("cargo:rustc-check-cfg=values({},\"{}\")", name, values);
+            }
         }
     }
 }