Review changes

Author: Kobzol

src/bootstrap/src/core/build_steps/perf.rs

@@ -27,7 +27,7 @@ Consider setting `rust.debuginfo-level = 1` in `config.toml`."#);
     let args = std::env::args().skip_while(|a| a != "--").skip(1);
 
     let mut cmd = builder.tool_cmd(Tool::RustcPerfWrapper);
-    cmd.env("PERF_RUSTC", rustc)
+    cmd.env("RUSTC_REAL", rustc)
         .env("PERF_COLLECTOR", collector)
         .env("PERF_RESULT_DIR", profile_results_dir)
         .args(args);

src/tools/rustc-perf-wrapper/README.md

@@ -1,3 +1,3 @@
 # rustc-perf wrapper
 Utility tool for invoking [`rustc-perf`](https://github.com/rust-lang/rustc-perf) for benchmarking/profiling
-a stage1/2 compiler built by bootstrap using `x run perf`.
+a stage1/2 compiler built by bootstrap using `x perf -- <command>`.

src/tools/rustc-perf-wrapper/src/main.rs

@@ -68,7 +68,7 @@ struct SharedOpts {
 #[derive(Debug, clap::Parser)]
 struct BuildContext {
     /// Compiler binary that will be benchmarked/profiled.
-    #[clap(long, hide = true, env = "PERF_RUSTC")]
+    #[clap(long, hide = true, env = "RUSTC_REAL")]
     compiler: PathBuf,
     /// rustc-perf collector binary that will be used for running benchmarks/profilers.
     #[clap(long, hide = true, env = "PERF_COLLECTOR")]