Can't install opencv4nodejs

1. I tried to install into RasberryPi.
2. I installed CMake already
3. I set
- `export OPENCV4NODEJS_DISABLE_AUTOBUILD=0`
- `export OPENCV4NODEJS_AUTOBUILD_OPENCV_VERSION=4.1.0`
4. I tried to install opencv4nodejs via `npm i opencv4nodejs`
5. I got the below error.

# Error Message

```
$ npm i opencv4nodejs

> opencv4nodejs@5.6.0 install /home/pi/opencv-virtualuvc/node_modules/opencv4nodejs
> node ./install/install.js

info the following opencv4nodejs environment variables are set in the package.json:
info autoBuildFlags: -DOPENCV_GENERATE_PKGCONFIG=ON -DOPENCV_PC_FILE_NAME=opencv.pc
info autoBuildOpencvVersion: 4.1.0
info install OPENCV_LIB_DIR is not set, looking for default lib dir
info install using lib dir: /usr/local/lib
/home/pi/opencv-virtualuvc/node_modules/opencv4nodejs/install/install.js:45
throw new Error('no OpenCV libraries found in lib dir: ' + libDir)
^

Error: no OpenCV libraries found in lib dir: /usr/local/lib
at Object. (/home/pi/opencv-virtualuvc/node_modules/opencv4nodejs/install/install.js:45:9)
at Module._compile (internal/modules/cjs/loader.js:778:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
at Module.load (internal/modules/cjs/loader.js:653:32)
at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
at Function.Module._load (internal/modules/cjs/loader.js:585:3)
at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
at startup (internal/bootstrap/node.js:283:19)
at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! opencv4nodejs@5.6.0 install: `node ./install/install.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the opencv4nodejs@5.6.0 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/pi/.npm/_logs/2020-06-19T22_35_51_386Z-debug.log
```

# Auto Build - Full Error Log

I'd like Auto Build. But I don't know where Auto Build Error Log is.

*OpenCV version* (example 3.4.1): ?.?.?

*With OpenCV-contrib?* (extra modules): ?

*OS*: Raspbian GNU/Linux 10 (buster)

```
$ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description: Raspbian GNU/Linux 10 (buster)
Release: 10
Codename: buster
```