Auto merge of #75431 - ehuss:platform-support, r=Mark-Simulacrum

Move platform support to the rustc book.

This moves the [Platform Support](https://forge.rust-lang.org/release/platform-support.html) page from the forge to the rustc book. There are several reasons for doing this:

* The forge is not really oriented towards end-users (it mostly contains infrastructure, governance and policy, internal team pages, etc.). This platform support page is useful to user to know which targets are supported.
* This page can now be updated in-sync with any PRs that add or remove a target, or change its status.
* This is now automatically checked on CI to verify the list does not get out of sync. Currently it only checks the presence/absence of an entry, but more sophisticated checks could be added in the future.

I'm not 100% certain this is the best location, but I think it fits. I'd like to see the rustc guide continue to grow, including things like linking information and more platform-specific details.

2 files changed, 45 insertions, 0 deletions

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index e13a5f24653..4b0905bd6c1 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -404,6 +404,7 @@ impl<'a> Builder<'a> {
                 test::CrateLibrustc,
                 test::CrateRustdoc,
                 test::Linkcheck,
+                test::TierCheck,
                 test::Cargotest,
                 test::Cargo,
                 test::Rls,
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index bb5b9296c0a..11e2564305f 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -2043,3 +2043,47 @@ impl Step for Bootstrap {
         run.builder.ensure(Bootstrap);
     }
 }
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub struct TierCheck {
+    pub compiler: Compiler,
+    target: TargetSelection,
+}
+
+impl Step for TierCheck {
+    type Output = ();
+    const DEFAULT: bool = true;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/tools/tier-check")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        let compiler = run.builder.compiler_for(run.builder.top_stage, run.host, run.host);
+        run.builder.ensure(TierCheck { compiler, target: run.host });
+    }
+
+    /// Tests the Platform Support page in the rustc book.
+    fn run(self, builder: &Builder<'_>) {
+        builder.ensure(compile::Std { compiler: self.compiler, target: self.target });
+        let mut cargo = tool::prepare_tool_cargo(
+            builder,
+            self.compiler,
+            Mode::ToolRustc,
+            self.target,
+            "run",
+            "src/tools/tier-check",
+            SourceType::InTree,
+            &[],
+        );
+        cargo.arg(builder.src.join("src/doc/rustc/src/platform-support.md"));
+        cargo.arg(&builder.rustc(self.compiler));
+        if builder.is_verbose() {
+            cargo.arg("--verbose");
+        }
+
+        builder.info("platform support check");
+        try_run(builder, &mut cargo.into());
+    }
+}