Remove obsolete clippy scripts.

Now that clippy is installable via rustup and is generally more stable,
we no longer need special scripts. `rustup component add clippy-preview` is
sufficient to install clippy, and `cargo clippy` is sufficient to run it.

Also, don't run clippy in test-all.sh. We do generally want to fix things
clippy reports, however it's not a requirement that the code be kept
clippy-warning-free at all times.

cranelift/test-all.sh

@@ -9,7 +9,7 @@ set -euo pipefail
 # - Make a release build.
 # - Run unit tests for all Rust crates (including the filetests)
 # - Build API documentation.
-# - Optionally, run clippy and fuzzing.
+# - Optionally, run fuzzing.
 #
 # All tests run by this script should be passing at all times.
 
@@ -70,14 +70,6 @@ cargo test --all
 banner "Rust documentation: $topdir/target/doc/cranelift/index.html"
 cargo doc
 
-# Run clippy if we have it.
-banner "Rust linter"
-if "$topdir/check-clippy.sh"; then
-    "$topdir/clippy-all.sh"
-else
-    echo "\`cargo +nightly install clippy\` for optional rust linting"
-fi
-
 # Ensure fuzzer works by running it with a single input
 # Note LSAN is disabled due to https://github.com/google/sanitizers/issues/764
 banner "cargo fuzz check"