Don't use rustup. Work around OpenBSD rustfmt bug.

Index: crates/rust-analyzer/tests/slow-tests/tidy.rs
--- crates/rust-analyzer/tests/slow-tests/tidy.rs.orig
+++ crates/rust-analyzer/tests/slow-tests/tidy.rs
@@ -14,17 +14,17 @@ fn check_code_formatting() {
     let sh = &Shell::new().unwrap();
     sh.change_dir(sourcegen::project_root());
 
-    let out = cmd!(sh, "rustup run stable rustfmt --version").read().unwrap();
-    if !out.contains("stable") {
-        panic!(
-            "Failed to run rustfmt from toolchain 'stable'. \
-                 Please run `rustup component add rustfmt --toolchain stable` to install it.",
-        )
+    let out = cmd!(sh, "rustfmt --version").read().unwrap();
+    // FIXME: OpenBSD's rustfmt doesn't report it's version correctly.
+    // At the time of writing, `rustfmt --version` gives `rustfmt 1.7.0-` (i.e. missing the
+    // `-stable` suffix.
+    if !out.contains("rustfmt") {
+        panic!("Failed to run rustfmt from toolchain 'stable'.");
     }
 
-    let res = cmd!(sh, "rustup run stable cargo fmt -- --check").run();
+    let res = cmd!(sh, "cargo fmt -- --check").run();
     if res.is_err() {
-        let _ = cmd!(sh, "rustup run stable cargo fmt").run();
+        let _ = cmd!(sh, "cargo fmt").run();
     }
     res.unwrap()
 }
