Auto merge of #138395 - Kobzol:ci-download-gcc, r=<try>

Download GCC from CI on test builders

This should reduce the duration of the `x86_64-gnu-llvm-18` job, which runs on PR CI, which is currently the only one that builds GCC (outside of the x64 dist builder).

Since we handle the GCC download in the GCC step, and not eagerly in config, we can set this flag globally across all test builders, as it won't do anything unless they actually try to build GCC.

Opening as a draft to test if it works on CI, because I still need to implement logic to avoid the download if there are any local modifications to GCC (essentially the "if-unchanged" mode, although I want to try something a bit different).

r? `@ghost`

Author: bors

config.example.toml

@@ -171,7 +171,7 @@
 # Note that this will attempt to download GCC even if there are local
 # modifications to the `src/gcc` submodule.
 # Currently, this is only supported for the `x86_64-unknown-linux-gnu` target.
-# download-ci-gcc = false
+#download-ci-gcc = false
 
 # =============================================================================
 # General build configuration options

src/bootstrap/src/bin/main.rs

@@ -1,20 +1,22 @@
+#![allow(unused)]
 //! bootstrap, the Rust build system
 //!
 //! This is the entry point for the build system used to compile the `rustc`
 //! compiler. Lots of documentation can be found in the `README.md` file in the
 //! parent directory, and otherwise documentation can be found throughout the `build`
 //! directory in each respective module.
 
-use std::fs::{self, OpenOptions};
-use std::io::{self, BufRead, BufReader, IsTerminal, Write};
-use std::str::FromStr;
-use std::{env, process};
-
 use bootstrap::{
     Build, CONFIG_CHANGE_HISTORY, Config, Flags, Subcommand, debug, find_recent_config_change_ids,
     human_readable_changes, t,
 };
 use build_helper::ci::CiEnv;
+use build_helper::git::get_closest_merge_commit;
+use std::fs::{self, OpenOptions};
+use std::io::{self, BufRead, BufReader, IsTerminal, Write};
+use std::process::Command;
+use std::str::FromStr;
+use std::{env, process};
 #[cfg(feature = "tracing")]
 use tracing::instrument;
 
@@ -34,7 +36,62 @@ fn main() {
     debug!("parsing config based on flags");
     let config = Config::parse(flags);
 
-    let mut build_lock;
+    let merge_commit1 =
+        get_closest_merge_commit(Some(&config.src), &config.git_config(), &[]).unwrap();
+    let merge_commit2 = String::from_utf8(
+        Command::new("git")
+            .args([
+                "rev-list",
+                &format!("--author=bors@rust-lang.org"),
+                "-n1",
+                "--first-parent",
+                "HEAD",
+            ])
+            .output()
+            .unwrap()
+            .stdout,
+    )
+    .unwrap();
+    let merge_commit3 = String::from_utf8(
+        Command::new("git")
+            .args([
+                "rev-list",
+                &format!("--author=bors@rust-lang.org"),
+                "-n1",
+                "--first-parent",
+                "HEAD^1",
+            ])
+            .output()
+            .unwrap()
+            .stdout,
+    )
+    .unwrap();
+    let current_commit = String::from_utf8(
+        Command::new("git").arg("rev-parse").arg("HEAD").output().unwrap().stdout,
+    )
+    .unwrap();
+    let git_history = String::from_utf8(
+        Command::new("git")
+            .arg("log")
+            .arg("--oneline")
+            .arg("-n")
+            .arg("20")
+            .arg("--pretty=format:%h %an %ae %s")
+            .output()
+            .unwrap()
+            .stdout,
+    )
+    .unwrap();
+    panic!(
+        r#"
+Merge commit1: {merge_commit1}
+Merge commit2: {merge_commit2}
+Merge commit3: {merge_commit3}
+HEAD: {current_commit}
+{git_history}"#
+    );
+
+    /*let mut build_lock;
     let _build_lock_guard;
 
     if !config.bypass_bootstrap_lock {
@@ -145,7 +202,7 @@ fn main() {
             let mut file = t!(OpenOptions::new().write(true).truncate(true).open(entry.path()));
             t!(file.write_all(lines.join("\n").as_bytes()));
         }
-    }
+    }*/
 }
 
 fn check_version(config: &Config) -> Option<String> {

src/ci/github-actions/jobs.yml

@@ -90,7 +90,7 @@ envs:
     # - not running `opt-dist`'s post-optimization smoke tests on the resulting toolchain
     #
     # If you *want* these to happen however, temporarily comment it before triggering a try build.
-    DIST_TRY_BUILD: 1
+#    DIST_TRY_BUILD: 1
 
   auto:
     <<: *production

src/ci/run.sh

@@ -179,6 +179,9 @@ else
     RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set llvm.static-libstdcpp"
   fi
 
+  # Download GCC from CI on test builders
+  RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set gcc.download-ci-gcc=true"
+
   if [ "$NO_DOWNLOAD_CI_RUSTC" = "" ]; then
     RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set rust.download-rustc=if-unchanged"
   fi