Auto merge of #145472 - Kobzol:bootstrap-dist, r=jieyouxu

Enforce in bootstrap that dist and install must have stage at least 1

This is a continuation of my efforts to fix staging in bootstrap after the stage0 redesign. This PR gets rid of all `compiler_for` usages in the `dist` steps 🎉 The only remaining usages are in the `test` steps, which are my next goal, and which will be the final boss.. both because they are quite tricky, and because most of the the rest of the steps have been already fixed.

The changes are relatively straightforward, `x dist` defaults to stage 2, so in that case we want to use a stage 1 build compiler for everything (except stdlib, but we usually use it even there because of uplifting).

What I didn't fix yet are the docs steps, because they are *very* implicit right now, and fixing them deserves its own PR.

The first commit reverts the tests that I accidentally removed in #145340 🤦‍♂️ I did it in this PR to avoid further git conflicts..

Best reviewed commit-by-commit.

r? `@jieyouxu`

try-job: dist-i686-linux
try-job: dist-armhf-linux
try-job: dist-x86_64-linux
try-job: dist-x86_64-msvc
try-job: dist-apple-various
try-job: dist-x86_64-apple

Author: bors

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

@@ -96,6 +96,30 @@ impl Std {
         }
         deps
     }
+
+    /// Returns true if the standard library will be uplifted from stage 1 for the given
+    /// `build_compiler` (which determines the stdlib stage) and `target`.
+    ///
+    /// Uplifting is enabled if we're building a stage2+ libstd, full bootstrap is
+    /// disabled and we have a stage1 libstd already compiled for the given target.
+    pub fn should_be_uplifted_from_stage_1(
+        builder: &Builder<'_>,
+        stage: u32,
+        target: TargetSelection,
+    ) -> bool {
+        stage > 1
+            && !builder.config.full_bootstrap
+            // This estimates if a stage1 libstd exists for the given target. If we're not
+            // cross-compiling, it should definitely exist by the time we're building a stage2
+            // libstd.
+            // Or if we are cross-compiling, and we are building a cross-compiled rustc, then that
+            // rustc needs to link to a cross-compiled libstd, so again we should have a stage1
+            // libstd for the given target prepared.
+            // Even if we guess wrong in the cross-compiled case, the worst that should happen is
+            // that we build a fresh stage1 libstd below, and then we immediately uplift it, so we
+            // don't pay the libstd build cost twice.
+            && (target == builder.host_target || builder.config.hosts.contains(&target))
+    }
 }
 
 impl Step for Std {
@@ -193,22 +217,7 @@ impl Step for Std {
         // Stage of the stdlib that we're building
         let stage = build_compiler.stage;
 
-        // If we're building a stage2+ libstd, full bootstrap is
-        // disabled and we have a stage1 libstd already compiled for the given target,
-        // then simply uplift a previously built stage1 library.
-        if build_compiler.stage > 1
-            && !builder.config.full_bootstrap
-            // This estimates if a stage1 libstd exists for the given target. If we're not
-            // cross-compiling, it should definitely exist by the time we're building a stage2
-            // libstd.
-            // Or if we are cross-compiling, and we are building a cross-compiled rustc, then that
-            // rustc needs to link to a cross-compiled libstd, so again we should have a stage1
-            // libstd for the given target prepared.
-            // Even if we guess wrong in the cross-compiled case, the worst that should happen is
-            // that we build a fresh stage1 libstd below, and then we immediately uplift it, so we
-            // don't pay the libstd build cost twice.
-            && (target == builder.host_target || builder.config.hosts.contains(&target))
-        {
+        if Self::should_be_uplifted_from_stage_1(builder, build_compiler.stage, target) {
             let build_compiler_for_std_to_uplift = builder.compiler(1, builder.host_target);
             builder.std(build_compiler_for_std_to_uplift, target);