fix: inline testnet-default-channel.js

web3.js/bin/localnet.sh

@@ -1,7 +1,18 @@
 #!/usr/bin/env bash
 set -e
 
-channel=$("$(dirname "$0")"/testnet-default-channel.js)
+channel=$(
+  cd "$(dirname "$0")";
+  node -p '
+    let p = [
+      "../lib/node_modules/@solana/web3.js/package.json",
+      "../@solana/web3.js/package.json",
+      "../package.json"
+    ].find(require("fs").existsSync);
+    if (!p) throw new Error("Unable to locate solana-web3.js directory");
+    require(p)["testnetDefaultChannel"]
+  '
+)
 
 usage() {
   exitcode=0