Auto merge of #18363 - paulrouget:fix_style_build, r=SimonSapin

use cargo manifest path to find build.py

Without this, build.py can't be found when servo is built as a dependency.

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components/style/build.rs

@@ -69,7 +69,8 @@ fn generate_properties() {
         }
     }
 
-    let script = Path::new(file!()).parent().unwrap().join("properties").join("build.py");
+    let script = Path::new(&env::var("CARGO_MANIFEST_DIR").unwrap())
+        .join("properties").join("build.py");
     let product = if cfg!(feature = "gecko") { "gecko" } else { "servo" };
     let status = Command::new(&*PYTHON)
         .arg(&script)