Add README describing the windows build process

davinci_build/windows/README.txt

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+
+
+If you're setting it up on a fresh windows system ...
+
+Download and install MSYS2, follow the directions on the website for updating
+pacman/packages
+https://msys2.github.io/
+
+
+good reference for pacman (and other package managers)
+https://wiki.archlinux.org/index.php/Pacman/Rosetta
+
+install the following (not all are strictly necessary but meh, and some
+probably pull in helpful/necessary stuff):
+=====================
+git
+subversion
+make
+gcc
+python
+python2
+pkgfile (for finding what packages provide a given file)
+
+libxml2-devel
+libreadline-devel
+libcurl-devel
+
+# for 64 bit, otherwise replace x86_64 with i686
+mingw-w64-x86_64-python2
+mingw-w64-x86_64-python3
+
+mingw-w64-x86_64-make
+mingw-w64-x86_64-gcc
+mingw-w64-x86_64-clang
+mingw-w64-x86_64-pkg-config
+
+
+mingw-w64-x86_64-libxml2
+mingw-w64-x86_64-libreadline
+mingw-w64-x86_64-hdf5
+mingw-w64-x86_64-curl
+
+...
+
+
+clone (or checkout) the repo
+cd to davinci_build/windows/dependencies/cfitsio
+
+./configure && make install
+
+back to source root dir
+
+./configure CXXFLAGS='-fpermissive' && make
+
+If you're on a VM that can take 15 minutes
+
+cd davinci_build/windows
+./make_win.sh ../..
+
+copy the exe dll and modules/ to the install directory
+(ie the folder contained what would go in C:/Program Files/Davinci)
+
+cd to parent of install directory and copy the nsi script there
+run NSIS on the script (after changing the defines at the top)
+
+Choose LZMA since it's the best compression
+
+
+
+