ci: fix check contract step

Author: bdeneux

Makefile.toml

@@ -92,7 +92,7 @@ env = { RUSTFLAGS = "-C link-arg=-s" }
 [tasks.check_contracts]
 dependencies = ["wasm"]
 script = '''
-cargo install --debug --version 1.0.0 --features iterator --example check_contract -- cosmwasm-vm
+if [[ ! -e ~/.cargo/bin/check_contract ]]; then cargo install --debug --version 1.0.0 --features iterator --force --example check_contract -- cosmwasm-vm ; fi
 for W in ./target/wasm32-unknown-unknown/release/*.wasm
 do
   echo -n "Checking `basename $W`... "