only emit c-string literals on Rust 1.79 and later (#4352) (#4353)

* only emit c-string literals on Rust 1.79 and later (#4352)

* add newsfragment

Author: Icxolu

newsfragments/4353.fixed.md

@@ -0,0 +1 @@
+fixed compile error due to c-string literals on Rust < 1.79

pyo3-build-config/src/lib.rs

@@ -143,7 +143,7 @@ pub fn print_feature_cfgs() {
         println!("cargo:rustc-cfg=invalid_from_utf8_lint");
     }
 
-    if rustc_minor_version >= 77 {
+    if rustc_minor_version >= 79 {
         println!("cargo:rustc-cfg=c_str_lit");
     }