Ubuntu OpenCV2 CMake Error at OpenCVDetectCXXCompiler.cmake

Ubuntu18.04编译安装OpenCV2.4.13，cmake时出错，错误如下：

CMake Error at cmake/OpenCVDetectCXXCompiler.cmake:85 (list):

list GET given empty list

Call Stack (most recent call first):

CMakeLists.txt:109 (include)

CMake Error at cmake/OpenCVDetectCXXCompiler.cmake:86 (list):

list GET given empty list

Call Stack (most recent call first):

CMakeLists.txt:109 (include)

CMake Error at cmake/OpenCVDetectCXXCompiler.cmake:89 (math):

math cannot parse the expression: "*100 + ": syntax error, unexpected

  exp_TIMES, expecting exp_OPENPARENT or exp_NUMBER (1)

Call Stack (most recent call first):

CMakeLists.txt:109 (include)

Detected version of GNU GCC: ()

解决方式：打开opencv2.4.13/cmake/ OpenCVDetectCXXCompiler.cmake，修改第67行"-dumpversion" 为 "-dumpfullversion"

原因是GCC版本太高了（>6），无法获取所有版本的编译器。

参考：https://github.com/opencv/opencv/pull/9430/files