build: factor out some utilities to build_tools_util.sh

contrib/build_tools_util.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+
+RED='\033[0;31m'
+BLUE='\033[0;34m'
+YELLOW='\033[0;33m'
+NC='\033[0m' # No Color
+function info {
+    printf "\r💬 ${BLUE}INFO:${NC}  ${1}\n"
+}
+function fail {
+    printf "\r🗯 ${RED}ERROR:${NC} ${1}\n"
+    exit 1
+}
+function warn {
+    printf "\r⚠️  ${YELLOW}WARNING:${NC}  ${1}\n"
+}
+
+
+# based on https://superuser.com/questions/497940/script-to-verify-a-signature-with-gpg
+function verify_signature() {
+    local file=$1 keyring=$2 out=
+    if out=$(gpg --no-default-keyring --keyring "$keyring" --status-fd 1 --verify "$file" 2>/dev/null) &&
+       echo "$out" | grep -qs "^\[GNUPG:\] VALIDSIG "; then
+        return 0
+    else
+        echo "$out" >&2
+        exit 1
+    fi
+}
+
+function verify_hash() {
+    local file=$1 expected_hash=$2
+    actual_hash=$(sha256sum $file | awk '{print $1}')
+    if [ "$actual_hash" == "$expected_hash" ]; then
+        return 0
+    else
+        echo "$file $actual_hash (unexpected hash)" >&2
+        rm "$file"
+        exit 1
+    fi
+}
+
+function download_if_not_exist() {
+    local file_name=$1 url=$2
+    if [ ! -e $file_name ] ; then
+        wget -O $file_name "$url"
+    fi
+}
+
+# https://github.com/travis-ci/travis-build/blob/master/lib/travis/build/templates/header.sh
+function retry() {
+  local result=0
+  local count=1
+  while [ $count -le 3 ]; do
+    [ $result -ne 0 ] && {
+      echo -e "\nThe command \"$@\" failed. Retrying, $count of 3.\n" >&2
+    }
+    ! { "$@"; result=$?; }
+    [ $result -eq 0 ] && break
+    count=$(($count + 1))
+    sleep 1
+  done
+
+  [ $count -gt 3 ] && {
+    echo -e "\nThe command \"$@\" failed 3 times.\n" >&2
+  }
+
+  return $result
+}