GNU Makefile - What needs to be done to go from Linux to make it run on Windows?

I have a GNU Makefile that already exists for a Linux C program.  What types of things need to be done to make the Makefile work on a Windows machine?

I ended up using Cygwin after-all because I found a command for windows batch file that can be used to send a series of commands to Cygwin with just requiring one instance of Cygwin open.  

The command I used in batch to access Cygwin is:

bash --login -c "command_1; command_2; ... command_N; exit; exec bash -rcfile exit"

I was misinformed from another thread that what I wanted to do cannot be accomplished with Cygwin, but when I figured it out I decided to use Cygwin instead of making my own version of windows makefile from a Linux makefile.