Realtime::Runner: fix compilation with MinGW

MinGW uses pthreads, not native Windows threads.
mkcollection: it's _WIN32, not WIN32
CMake: further confine MSVC-specific link flags to MSVC
CMake: update output directory definition

Replace deprecated CMake variables with modern ones.
fix export.h for MinGW
link marsyasqt5 library to marsyas library (needed with MinGW)