sync llvm submodule during config parse

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

Author: onur-ozkan

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

@@ -2729,6 +2729,10 @@ impl Config {
         download_ci_llvm: Option<StringOrBool>,
         asserts: bool,
     ) -> bool {
+        // Initialize the llvm submodule if not initialized already.
+        // If submodules are disabled, this does nothing.
+        self.update_submodule("src/llvm-project");
+
         let if_unchanged = || {
             // Git is needed to track modifications here, but tarball source is not available.
             // If not modified here or built through tarball source, we maintain consistency