build: use share cargo target dir for both clippy and integration test

Author: tesuji

ci/integration-tests.sh

@@ -5,6 +5,9 @@ if [[ -z "$INTEGRATION" ]]; then
     exit 0
 fi
 
+CARGO_TARGET_DIR=$(pwd)/target
+export CARGO_TARGET_DIR
+
 rm ~/.cargo/bin/cargo-clippy
 cargo install --force --debug --path .