EasyPR failed to Setup on MSVC

Nobody has claimed this yet.

**I'm submitting a ...** (check one with "x")

```
[] bug report
[x ] help wanted
[x] feature request
```

**Current behavior**
setup failed

**Expected/desired behavior**
setup successfully

**Reproduction of the problem**
1.git clone https://github.com/liuruoze/EasyPR F:\gitP\liuruoze\EasyPR
2.cd F:\gitP\liuruoze\EasyPR\build_amd64
3.cmake -G "Visual Studio 16 2019" -A x64 -DCMAKE_SYSTEM_VERSION=10.0.18362.0 -DOpenCV_DIR=F:\tools\opencv\build\x64\vc14\lib -DCMAKE_BUILD_TYPE=Release .. 2>&1

**Error info:**
CMake Error at CMakeLists.txt:60 (add_executable):
The target name "test/main.cpp" is reserved or not valid for certain CMake
features, such as generator expressions, and may result in undefined
behavior.

**log**
[configure.log](https://github.com/liuruoze/EasyPR/files/9336220/configure.log)

If the current behavior is a bug or you can illustrate your feature request better with an example, please provide the steps to reproduce.

**What is the expected behavior?**

setup successfully

**What is the motivation / use case for changing the behavior?**

**Please tell us about your environment:**
VS 2019 + Windows Server 2019

Start with CMakeLists.txt at line 60 and reproduce the configuration from the build_amd64 directory using the Visual Studio 16 2019 generator and the supplied OpenCV_DIR. Verify that CMake configuration completes successfully on VS 2019 and Windows Server 2019 without the invalid target-name error.

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