Update to cranelift's formatting and testing scripts.

check-clippy.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+set -euo pipefail
+
+# Usage: check-clippy.sh
+
+if cargo install --list | tee /dev/null | grep -q "^clippy v0"; then
+    exit 0
+else
+    exit 1
+fi