downgrade build msg to debug msg (#142)

Author: ZuseZ4

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -619,7 +619,7 @@ pub(crate) fn run_pass_manager(
         // We will run this again with different values in the context of automatic differentiation.
         let first_run = true;
         let noop = false;
-        dbg!("running llvm pm opt pipeline");
+        debug!("running llvm pm opt pipeline");
         write::llvm_optimize(cgcx, dcx, module, config, opt_level, opt_stage, first_run, noop)?;
     }
     debug!("lto done");