MINIFI-368 exclude hidden files when scanning for src files

[Andy Christianson-2]

MiNiFi cpp team,


I have submitted a PR which fixes an issue where having a file open in vim causes the cmake build to fail. It fails because the BuildTests.cmake file includes hidden files in its scan for source files.


Please have a look at https://github.com/apache/nifi-minifi-cpp/pull/125? and merge in when possible.


-Andy C.