fix: move default rust_std_features to config

Author: shrirambalaji

src/bootstrap/src/core/config/config.rs

@@ -2096,7 +2096,8 @@ impl Config {
             );
         }
 
-        config.rust_std_features = std_features.unwrap_or_default();
+        let default_std_features = BTreeSet::from([String::from("panic-unwind")]);
+        config.rust_std_features = std_features.unwrap_or(default_std_features);
 
         let default = debug == Some(true);
         config.rust_debug_assertions = debug_assertions.unwrap_or(default);

src/bootstrap/src/lib.rs

@@ -666,8 +666,6 @@ impl Build {
         let mut features: BTreeSet<&str> =
             self.config.rust_std_features.iter().map(|s| s.as_str()).collect();
 
-        features.insert("panic-unwind");
-
         match self.config.llvm_libunwind(target) {
             LlvmLibunwind::InTree => features.insert("llvm-libunwind"),
             LlvmLibunwind::System => features.insert("system-llvm-libunwind"),