opt-dist: rebuild rustc when doing static LLVM builds

when building LLVM it's obvious that in case of shared build rustc doesn't need to be recompiled,
but with static builds it would be better to compile rustc again to ensure we linked proper library.
maybe I didn't understand the pipeline correctly, but it was strange for me to see that in Stage 5
LLVM is built while rustc is not

Author: ognevny

src/tools/opt-dist/src/main.rs

@@ -343,8 +343,11 @@ fn execute_pipeline(
 
     let mut dist = Bootstrap::dist(env, &dist_args)
         .llvm_pgo_optimize(&llvm_pgo_profile)
-        .rustc_pgo_optimize(&rustc_pgo_profile)
-        .avoid_rustc_rebuild();
+        .rustc_pgo_optimize(&rustc_pgo_profile);
+
+    if env.supports_shared_llvm() {
+        dist = dist.avoid_rustc_rebuild()
+    }
 
     for bolt_profile in bolt_profiles {
         dist = dist.with_bolt_profile(bolt_profile);