Your CMakeLists file in the base folder should not be changed. But rather in the src folder CMakeList you should add the following line:

```
target_include_directories( tokenauction PUBLIC "$ENV{BOOST_DIR}/include" )
```

Where BOOST_DIR is an environmental variable pointing to your boost folder. On my computer it is:
`/home/eosio/1.8/src/boost_1_70_0`