Rollup merge of rust-lang#147332 - Shunpoco:fast-spellcheck, r=Kobzol

Set opt-level flag for installing tool only on CI

## Context
ensure_version_or_cargo_install uses -Copt-level=0 for quicker installation. However, the flag affects the tool's performance. For example, typos-cli with opt-level=0 takes 15 seconds for checking /compiler on my local, but the tool with default opt-level only takes less than 1 sec.

It fixes rust-lang#147331

## Changes
This PR enables the option only when the test tidy is run on CI.
We've discussed that opt-level=1 should be enough, so I also change the level from 0 to 1.

Author: workingjubilee

src/tools/tidy/src/lib.rs

@@ -194,8 +194,8 @@ pub fn ensure_version_or_cargo_install(
     // use --force to ensure that if the required version is bumped, we update it.
     // use --target-dir to ensure we have a build cache so repeated invocations aren't slow.
     // modify PATH so that cargo doesn't print a warning telling the user to modify the path.
-    let cargo_exit_code = Command::new(cargo)
-        .args(["install", "--locked", "--force", "--quiet"])
+    let mut cmd = Command::new(cargo);
+    cmd.args(["install", "--locked", "--force", "--quiet"])
         .arg("--root")
         .arg(&tool_root_dir)
         .arg("--target-dir")
@@ -208,10 +208,16 @@ pub fn ensure_version_or_cargo_install(
                     .chain(std::iter::once(tool_bin_dir.clone())),
             )
             .expect("build dir contains invalid char"),
-        )
-        .env("RUSTFLAGS", "-Copt-level=0")
-        .spawn()?
-        .wait()?;
+        );
+
+    // On CI, we set opt-level flag for quicker installation.
+    // Since lower opt-level decreases the tool's performance,
+    // we don't set this option on local.
+    if CiEnv::is_ci() {
+        cmd.env("RUSTFLAGS", "-Copt-level=0");
+    }
+
+    let cargo_exit_code = cmd.spawn()?.wait()?;
     if !cargo_exit_code.success() {
         return Err(io::Error::other("cargo install failed"));
     }