make the config lld test parameter smoother to work, and have no_llvm_config set even when target_config is not present

Author: Shourya742

src/bootstrap/src/core/config/toml/rust.rs

@@ -409,23 +409,24 @@ pub(crate) fn validate_codegen_backends(backends: Vec<String>, section: &str) ->
     }
     backends
 }
+
 #[cfg(not(test))]
-fn default_lld_opt_in_targets() -> &'static [&'static str] {
-    &["x86_64-unknown-linux-gnu"]
+fn default_lld_opt_in_targets() -> Vec<String> {
+    vec!["x86_64-unknown-linux-gnu".to_string()]
 }
 
 #[cfg(test)]
 thread_local! {
-    static TEST_LLD_OPT_IN_TARGETS: std::cell::RefCell<Option<&'static [&'static str]>> = std::cell::RefCell::new(None);
+    static TEST_LLD_OPT_IN_TARGETS: std::cell::RefCell<Option<Vec<String>>> = std::cell::RefCell::new(None);
 }
 
 #[cfg(test)]
-fn default_lld_opt_in_targets() -> &'static [&'static str] {
-    TEST_LLD_OPT_IN_TARGETS.with(|cell| cell.borrow().unwrap_or(&[]))
+fn default_lld_opt_in_targets() -> Vec<String> {
+    TEST_LLD_OPT_IN_TARGETS.with(|cell| cell.borrow().clone()).unwrap_or_default()
 }
 
 #[cfg(test)]
-pub fn with_lld_opt_in_targets<R>(targets: &'static [&'static str], f: impl FnOnce() -> R) -> R {
+pub fn with_lld_opt_in_targets<R>(targets: Vec<String>, f: impl FnOnce() -> R) -> R {
     TEST_LLD_OPT_IN_TARGETS.with(|cell| {
         let prev = cell.replace(Some(targets));
         let result = f();
@@ -633,13 +634,13 @@ impl Config {
         //   thus, disabled
         // - similarly, lld will not be built nor used by default when explicitly asked not to, e.g.
         //   when the config sets `rust.lld = false`
-        if default_lld_opt_in_targets().contains(&self.host_target.triple.to_string().as_str())
+        if default_lld_opt_in_targets().contains(&self.host_target.triple.to_string())
             && self.hosts == [self.host_target]
         {
             let no_llvm_config = self
                 .target_config
                 .get(&self.host_target)
-                .is_some_and(|target_config| target_config.llvm_config.is_none());
+                .is_none_or(|target_config| target_config.llvm_config.is_none());
             let enable_lld = self.llvm_from_ci || no_llvm_config;
             // Prefer the config setting in case an explicit opt-out is needed.
             self.lld_enabled = lld_enabled.unwrap_or(enable_lld);