wxwidgets use script: wxBase requires pthreads lib
wxwidgets use script: wxBase requires pthreads lib

* still not sure if we need to add wxWidgets_CXX_FLAGS (-pthread) to CMAKE_CXX_FLAGS
* https://stackoverflow.com/questions/2127797/significance-of-pthread-flag-when-compiling
* holding off, hoping we don't have to modify global CMAKE_CXX_FLAGS - cmake is ready to go, just commented-out
* see issue https://github.com/smanders/externpro/issues/194#issuecomment-398804739

smanders/externpro