ubuntu18 编译maplab opencv3_catkin 时出现Flow control statements are not properly nested.

问题

CMake Error at cmake/OpenCVCompilerOptions.cmake:21 (else):
Flow control statements are not properly nested.
打开对应的cmake文件21行发现同一个作用域有两个else

解决方法

21行22行注释掉就可以了
别的电脑也编译过貌似没出现过这种问题，应该与cmake版本有关