Add generate precompile script to fix CGO flags issue (#489)

scripts/generate_precompile.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+set -e
+
+# This script generates a Stateful Precompile stub based off of a Solidity ABI file.
+# It first sets the necessary CGO_FLAGs for the BLST library used in AvalancheGo and
+# then runs PrecompileGen.
+if ! [[ "$0" =~ scripts/generate_precompile.sh ]]; then
+  echo "must be run from repository root, but got $0"
+  exit 255
+fi
+
+# Load the versions
+SUBNET_EVM_PATH=$(
+  cd "$(dirname "${BASH_SOURCE[0]}")"
+  cd .. && pwd
+)
+
+# Load the constants
+source "$SUBNET_EVM_PATH"/scripts/constants.sh
+
+go run ./cmd/precompilegen/main.go $@