CMake: Copy source files into binary dir

[1480c1]

Same as https://github.com/MediaArea/ZenLib/pull/105

A work around for certain compilers not working on windows due to extra long paths (Something like CMakeFiles/mediainfo.dir/D_/actions/_work/media-autobuild_suite/media-autobuild_suite/build/libmediainfo-git/Source/ThirdParty/aes-gladman/aes_modes.c.o under D:/actions/_work/media-autobuild_suite/media-autobuild_suite/build/libmediainfo-git/build)

Since it the source files aren't subdirectories, cmake uses absolute paths to the files when deciding the output name.