Makefile bug fix for opencv4.

[tkameyama]

Description

fix Build with opencv4 to use USE_OPENCV_INC_PATH.

Currently OPENCV_INC_PATH is used as following:

CFLAGS += -I$(USE_OPENCV_INC_PATH)/include

And the program is used opencv header files as follows:

#include <opencv2/opencv.hpp>

But opencv4 is installed header file to include/opencv4/opencv2. So we cannot specify ijnclude path by OPENCV_INC_PATH. This PR is enable opencv4 include path by OPENCV_INC_PATH.

[mxnet-bot]

Hey @tkameyama , Thanks for submitting the PR All tests are already queued to run once. If tests fail, you can trigger one or more tests again with the following commands:

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[leezu]

We'll delete the Makefile build prior to MXNet 2 release, so I suggest this PR should target the 1.x branch? Is there any problem why you can't use the cmake build on master?

[tkameyama]

I change target to 1.x branch.

[leezu]

Thanks @tkameyama. There are some CI issues on 1.x. We'll resolve them first and then retrigger the CI for your PR

[leezu]

@mxnet-bot run ci [all]

[mxnet-bot]

Jenkins CI successfully triggered : [centos-gpu, centos-cpu, edge, unix-cpu, website, windows-gpu, windows-cpu, unix-gpu, sanity, clang, miscellaneous]