fetch submodule before checking llvm stamp

Previously, we were checking the LLVM stamp before fetching the submodule
which leads to not being able to compile llvm on submodule updates.

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

Author: onur-ozkan

src/bootstrap/src/core/build_steps/llvm.rs

@@ -259,6 +259,8 @@ impl Step for Llvm {
 
     /// Compile LLVM for `target`.
     fn run(self, builder: &Builder<'_>) -> LlvmResult {
+        builder.update_submodule(&Path::new("src").join("llvm-project"));
+
         let target = self.target;
         let target_native = if self.target.starts_with("riscv") {
             // RISC-V target triples in Rust is not named the same as C compiler target triples.
@@ -279,7 +281,6 @@ impl Step for Llvm {
             Err(m) => m,
         };
 
-        builder.update_submodule(&Path::new("src").join("llvm-project"));
         if builder.llvm_link_shared() && target.is_windows() {
             panic!("shared linking to LLVM is not currently supported on {}", target.triple);
         }