build: configure min const generics

build.rs

@@ -854,9 +854,17 @@ fn configure(interpreter_config: &InterpreterConfig) -> Result<()> {
         println!("cargo:rustc-cfg=Py_3_{}", i);
     }
 
+    configure_min_const_generics();
+
     Ok(())
 }
 
+fn configure_min_const_generics() {
+    if rustc_minor_version().unwrap_or(0) >= 51 {
+        println!("cargo:rustc-cfg=min_const_generics");
+    }
+}
+
 fn check_target_architecture(interpreter_config: &InterpreterConfig) -> Result<()> {
     // Try to check whether the target architecture matches the python library
     let rust_target = match cargo_env_var("CARGO_CFG_TARGET_POINTER_WIDTH")
@@ -922,7 +930,7 @@ fn configure_abi3_without_interpreter() {
 }
 
 fn rustc_minor_version() -> Option<u32> {
-    let rustc = env::var_os("RUSTC")?;
+    let rustc = env_var("RUSTC")?;
     let output = Command::new(rustc).arg("--version").output().ok()?;
     let version = core::str::from_utf8(&output.stdout).ok()?;
     let mut pieces = version.split('.');
@@ -932,12 +940,6 @@ fn rustc_minor_version() -> Option<u32> {
     pieces.next()?.parse().ok()
 }
 
-fn manage_min_const_generics() {
-    if rustc_minor_version().unwrap_or(0) >= 51 {
-        println!("cargo:rustc-cfg=min_const_generics");
-    }
-}
-
 fn main_impl() -> Result<()> {
     // If PYO3_NO_PYTHON is set with abi3, we can build PyO3 without calling Python.
     // We only check for the abi3-py3{ABI3_MAX_MINOR} because lower versions depend on it.
@@ -974,8 +976,6 @@ fn main_impl() -> Result<()> {
         println!("cargo:rustc-cfg={}=\"{}\"", CFG_KEY, flag)
     }
 
-    manage_min_const_generics();
-
     Ok(())
 }