Unable to build without IDA

Running cmake with `-DBINEXPORT_ENABLE_IDAPRO=OFF` results in the error:

```
CMake Error at build/binexport/cmake/FindIdaSdk.cmake:173 (find_path):
  Could not find IdaSdk_LIBPATH64 using the following files: libida64.so
Call Stack (most recent call first):
  cmake/BinDiffDeps.cmake:32 (find_package)
  CMakeLists.txt:49 (include)
```