Freetype CI error

[lz1998]

Description

I create a pull request to add freetype. PR

• CircleCI: Your tests passed on CircleCI!
• AppVeyor: build failed https://ci.appveyor.com/project/deadprogram/gocv/builds/40056732

How to pass AppVeyor check?

Steps to Reproduce

1. Add freetype #873

Your Environment

• Operating System and version: AppVeyor windows/amd64
• OpenCV version used: 4.5.x
• How did you install OpenCV? Yes
• GoCV version used: PR
• Go version: 1.13
• Did you run the env.sh or env.cmd script before trying to go run or go build? No