stdout doesn't print to console in real-time while debugging

Hi,

I'm using Catch2 to do unit testing. When I use gdb to debug the test case, std::cout doesn't print to console immediately, it seems the logs are redirected somewhere and are printed all together when the test case finishes. The issue is quite similar to #49. But I didn't find a solution. Could share your solution to the problem? @philsquared Thank you!