add support for compile-time if/if-not CI check

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Author: onur-ozkan

src/bootstrap/build.rs

@@ -4,4 +4,10 @@ fn main() {
     let host = env::var("HOST").unwrap();
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rustc-env=BUILD_TRIPLE={host}");
+
+    println!("cargo::rerun-if-env-changed=GITHUB_ACTIONS");
+    println!("cargo::rustc-check-cfg=cfg(ci)");
+    if env::var("GITHUB_ACTIONS").is_ok() {
+        println!("cargo:rustc-cfg=ci");
+    }
 }