Revert "opt-dist: dont overrwite config.toml when verifying"

This reverts commit c81a40b.

This commit appears to have changed which rustc and cargo versions are
used for some areas of tooling, which meant it was not possible to do a
beta bump.

Revert to test.

Discussion: https://rust-lang.zulipchat.com/#narrow/stream/241545-t-release/topic/1.2E81.20stage0.20bump

Author: tgross35

src/tools/opt-dist/src/tests.rs

@@ -60,17 +60,26 @@ pub fn run_tests(env: &Environment) -> anyhow::Result<()> {
         .join(format!("llvm-config{}", executable_extension()));
     assert!(llvm_config.is_file());
 
-    let rustc = format!("build.rustc={}", rustc_path.to_string().replace('\\', "/"));
-    let cargo = format!("build.cargo={}", cargo_path.to_string().replace('\\', "/"));
-    let llvm_config =
-        format!("target.{host_triple}.llvm-config={}", llvm_config.to_string().replace('\\', "/"));
+    let config_content = format!(
+        r#"profile = "user"
+change-id = 115898
 
-    log::info!("Set the following configurations for running tests:");
-    log::info!("\t{rustc}");
-    log::info!("\t{cargo}");
-    log::info!("\t{llvm_config}");
+[build]
+rustc = "{rustc}"
+cargo = "{cargo}"
+
+[target.{host_triple}]
+llvm-config = "{llvm_config}"
+"#,
+        rustc = rustc_path.to_string().replace('\\', "/"),
+        cargo = cargo_path.to_string().replace('\\', "/"),
+        llvm_config = llvm_config.to_string().replace('\\', "/")
+    );
+    log::info!("Using following `config.toml` for running tests:\n{config_content}");
 
     // Simulate a stage 0 compiler with the extracted optimized dist artifacts.
+    std::fs::write("config.toml", config_content)?;
+
     let x_py = env.checkout_path().join("x.py");
     let mut args = vec![
         env.python_binary(),
@@ -89,12 +98,6 @@ pub fn run_tests(env: &Environment) -> anyhow::Result<()> {
         "tests/run-pass-valgrind",
         "tests/ui",
         "tests/crashes",
-        "--set",
-        &rustc,
-        "--set",
-        &cargo,
-        "--set",
-        &llvm_config,
     ];
     for test_path in env.skipped_tests() {
         args.extend(["--skip", test_path]);