Unrolled build for #145073

Rollup merge of #145073 - ZuseZ4:autodiff-llvm-21, r=jieyouxu

update enzyme submodule to handle llvm 21

This currently has a fix / workaround in our local rust-lang/Enzyme fork, which is needed to unblock a few people contributing to std::autodiff. It also permanently disables a component (BCLoader) which we shouldn't need on the rust side, hence saving a bit of compile time and disk space.

Once upstream Enzyme (EnzymeAD/Enzyme) fixed llvm-21 support I'll probably make another pr to drop our local patch.

Author: rust-timer

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

@@ -986,6 +986,7 @@ impl Step for Enzyme {
             .env("LLVM_CONFIG_REAL", &llvm_config)
             .define("LLVM_ENABLE_ASSERTIONS", "ON")
             .define("ENZYME_EXTERNAL_SHARED_LIB", "ON")
+            .define("ENZYME_BC_LOADER", "OFF")
             .define("LLVM_DIR", builder.llvm_out(target));
 
         cfg.build();