Merge pull request #3724 from davidhewitt/fix-build-config-issue

re-add emit_pyo3_cfgs for pyo3 0.20.0 compatibility

Author: adamreichold

pyo3-build-config/src/impl_.rs

@@ -153,6 +153,13 @@ pub struct InterpreterConfig {
 }
 
 impl InterpreterConfig {
+    #[doc(hidden)]
+    pub fn emit_pyo3_cfgs(&self) {
+        for cfg in self.build_script_outputs() {
+            println!("{}", cfg);
+        }
+    }
+
     #[doc(hidden)]
     pub fn build_script_outputs(&self) -> Vec<String> {
         // This should have been checked during pyo3-build-config build time.