- docs.rs detection when built as dependency

build.rs

@@ -115,7 +115,9 @@ fn fix_xwin_lib_case() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    if env::var("DOCS_RS").is_err() {
+    if env::var("DOCS_RS").is_ok() {
+        println!("cargo::rustc-cfg=docsrs");
+    } else {
         let host = env::var("HOST")?;
         let target = env::var("TARGET")?;
         let is_cross = host != target