Revert "Delete dummy.txt"

This reverts commit 963f71baeface9826bc0184b61c758487fb6e8ad.
Revert "Update makefile"

This reverts commit fef6d582d2e9683b367d33911fe407c189280a72.
Revert "Set up CC/CXX/LD to be more flexible (for Mingw building)"

This reverts commit ddd169008980351d77c8371b04afa9b1ba8d6c0b.