Build fails with OPENCV4NODEJS_DISABLE_AUTOBUILD=1

# Error Message

```
> opencv-build@0.0.17 install /usr/src/app/node_modules/opencv-build
> node ./install.js

info install OPENCV4NODEJS_DISABLE_AUTOBUILD is set
info install skipping auto build...

> opencv4nodejs@4.14.1 install /usr/src/app/node_modules/opencv4nodejs
> node-gyp rebuild

make: Entering directory '/usr/src/app/node_modules/opencv4nodejs/build'
CXX(target) Release/obj.target/opencv4nodejs/cc/opencv4nodejs.o
In file included from ../cc/CustomMatAllocator.h:8:0,
from ../cc/ExternalMemTracking.h:2,
from ../cc/opencv4nodejs.cc:2:
../cc/core/Size.h:1:28: fatal error: opencv2/core.hpp: No such file or directory
#include
^
compilation terminated.
make: *** [Release/obj.target/opencv4nodejs/cc/opencv4nodejs.o] Error 1
opencv4nodejs.target.mk:227: recipe for target 'Release/obj.target/opencv4nodejs/cc/opencv4nodejs.o' failed
make: Leaving directory '/usr/src/app/node_modules/opencv4nodejs/build'
gyp ERR! build error
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack at ChildProcess.onExit (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/build.js:262:23)
gyp ERR! stack at ChildProcess.emit (events.js:189:13)
gyp ERR! stack at Process.ChildProcess._handle.onexit (internal/child_process.js:248:12)
gyp ERR! System Linux 4.9.125-linuxkit
gyp ERR! command "/usr/local/bin/node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /usr/src/app/node_modules/opencv4nodejs
gyp ERR! node -v v10.15.3
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok

```

# Auto Build - Full Error Log

N/A

# Manual Build - Environment Information

*OpenCV version*

Built from source, using the following commands:

```
git clone --progress --verbose https://github.com/opencv/opencv.git
cd opencv
mkdir build
cd build
cmake -D CMAKE_BUILD_TYPE=RELEASE -D BUILD_EXAMPLES=OFF -D BUILD_DOCS=OFF -D BUILD_PERF_TESTS=OFF -D BUILD_TESTS=OFF -D CMAKE_INSTALL_PREFIX=/usr/local ..
make install
```

This _appears_ to create include paths that look like `/usr/local/include/opencv4/opencv2/`

*With OpenCV-contrib?* (extra modules): No

*OS*: This is in a Docker build, with `FROM node:10`. I _believe_ that's Ubuntu (?)