update std uplifting algorithm

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

Author: onur-ozkan

src/bootstrap/src/core/build_steps/compile.rs

@@ -191,10 +191,17 @@ impl Step for Std {
 
  let mut target_deps = builder.ensure(StartupObjects { compiler, target });
 
- let compiler_to_use = builder.compiler_for(compiler.stage, compiler.host, target);
+ let mut compiler_to_use = builder.compiler_for(compiler.stage, compiler.host, target);
  trace!(?compiler_to_use);
 
- if compiler_to_use != compiler {
+ if compiler_to_use != compiler
+ // Never uplift std unless we have compiled stage 2; if stage 2 is compiled,
+ // uplift it from there.
+ //
+ // FIXME: improve `fn compiler_for` to avoid adding stage condition here.
+ && compiler.stage > 2
+ {
+ compiler_to_use.stage = 2;
  trace!(?compiler_to_use, ?compiler, "compiler != compiler_to_use, uplifting library");
 
  builder.ensure(Std::new(compiler_to_use, target));