Always ignore build failure of failable tools (rls, rustfmt, clippy, miri).

If build failed for these tools, they will be automatically skipped from
distribution, and will not fail the whole build.

Test failures are *not* ignored, nor build failure of other tools (e.g.
cargo). Therefore it should have no observable effect to the current CI
system.

This is step 1/8 of automatic management of broken tools #45861.

src/bootstrap/dist.rs

@@ -1083,7 +1083,8 @@ fn run(self, builder: &Builder) -> Option<PathBuf> {
         let rls = builder.ensure(tool::Rls {
             compiler: builder.compiler(stage, build.build),
             target
-        }).expect("Rls to build: toolstate is testing");
+        }).or_else(|| { println!("Unable to build RLS, skipping dist"); None })?;
+
         install(&rls, &image.join("bin"), 0o755);
         let doc = image.join("share/doc/rls");
         install(&src.join("README.md"), &doc, 0o644);
@@ -1167,11 +1168,12 @@ fn run(self, builder: &Builder) -> Option<PathBuf> {
         let rustfmt = builder.ensure(tool::Rustfmt {
             compiler: builder.compiler(stage, build.build),
             target
-        }).expect("Rustfmt to build: toolstate is testing");
+        }).or_else(|| { println!("Unable to build Rustfmt, skipping dist"); None })?;
         let cargofmt = builder.ensure(tool::Cargofmt {
             compiler: builder.compiler(stage, build.build),
             target
-        }).expect("Cargofmt to build: toolstate is testing");
+        }).or_else(|| { println!("Unable to build Cargofmt, skipping dist"); None })?;
+
         install(&rustfmt, &image.join("bin"), 0o755);
         install(&cargofmt, &image.join("bin"), 0o755);
         let doc = image.join("share/doc/rustfmt");

src/bootstrap/tool.rs

@@ -11,7 +11,7 @@
 use std::fs;
 use std::env;
 use std::path::PathBuf;
-use std::process::Command;
+use std::process::{Command, exit};
 
 use Mode;
 use Compiler;
@@ -115,7 +115,14 @@ fn run(self, builder: &Builder) -> Option<PathBuf> {
         println!("Building stage{} tool {} ({})", compiler.stage, tool, target);
 
         let mut cargo = prepare_tool_cargo(builder, compiler, target, "build", path);
-        build.run_expecting(&mut cargo, expectation);
+        if !build.try_run(&mut cargo, expectation) {
+            if expectation == BuildExpectation::None {
+                exit(1);
+            } else {
+                return None;
+            }
+        }
+
         if expectation == BuildExpectation::Succeeding || expectation == BuildExpectation::None {
             let cargo_out = build.cargo_out(compiler, Mode::Tool, target)
                 .join(exe(tool, &compiler.host));