Nit on windows

The support on windows is more than experimental. Fell free to report your attempts.

Using msys2

msys2 and mingw-w64 package tools and services to compile native Windows applications using GCC and the GNU toolchain.

Download and install msys2 by following the instructions at https://msys2.github.io/.

Install the minimum required package to download and compile Nit:

pacman -S make git ccache pkg-config libgc-devel libcurl-devel diffutils mingw-w64-x86_64-gc mingw-w64-x86_64-libunwind mingw-w64-x86_64-pcre mingw-w64-x86_64-libsystre mingw-w64-x86_64-dlfcn mingw-w64-x86_64-pkg-config mingw-w64-x86_64-curl

We use two regex related packages, -pcre provides libpcreposix.so and -libsystre provides regex.h. It is not ideal, but it works.

Then, from the msys2 (or mingw64) command line, clone the Nit repo as usual:
```
git clone https://github.comnitlangnit.git
```
Compile the Nit tools with:
```
GC_MARKERS1 make
```
As suggested by the previous make call, setup your environment with:
```
source miscnit_env.sh install
```
To test the compiler at bin/nitc.exe, compile and execute hello_world.exe with:
```
nitc exampleshello_world.nit
./hello_world.exe
```
To distribute a program, copy the required DLL files local to mingw64. For hello_world.exe, a call to ldd hello_world.exe lists the following files which must be copied:
```
C:\msys64mingw64binlibgc-1.dll
C:\msys64mingw64binlibwinpthread-1.dll
C:\msys64mingw64binlibpcreposix-0.dll
```

Issues

If the compiled Nit program hangs, it may be an issue with libgc. A workaround is to set the env var GC_MARKER to 1, which prevents a deadlock between the many GC threads.

GC_MARKERS=1 bin/nitc examples/hello_world.nit

See: https://github.com/Alexpux/MINGW-packages/issues/1110
Some modules, including glesv2 and egl, do not need the pkgconfig annotation on Windows. You may have to remove the line pkgconfig from these modules to compile them and their clients.

Using Cygwin

Download Cygwin from https://cygwin.com/

Install it and select the following packages:

gcc-core gcc-g+ git make ccache pkg-config libisl10 libcloog-isl libgc-devel

Then, from the cygwin command line, clone the Nit repo as usual:
```
git clone https://github.comnitlangnit.git
```
It will complain about the "very bad name" test file. This file cannot be represented on a Windows FS. Ignore this message, all other thousands of files should have unpacked successfully. To clear the repository and have a nice working dir status (if you care), you should run:
```
git chechout -f HEAD
```
As proposed by the output of the make, setup your environment with
```
source miscnit_env.sh
```
When you finally have a bin/nitc.exe, compile and execute hello_world with:
```
nitc exampleshello_world.nit
./hello_world.exe
```
To distribute a program outside of the cygwin environment, copy the cygwin and libgc DDLs with the executable. More DLLs may be needed for programs using native libraries, but for hello_world.exe and nitc.exe only the following libraries are needed:

/usr/bin/cyggc-1.dll /usr/bin/cygwin1.dll
More work is needed to actually develop Nit programs under a Windows environment. Simple programs like hello_world and Fibonacci work well outside of cygwin. However the compiler still expects UNIX-like paths and can't find nit_dir.

Additional notes:

I didn't find libunwind for cygwin, but I didn't search much either.

Cygwin FAQ/issues

The initial make does not work

If you have something like:
```
srcgit-gen-version.sh: line 2: $'\r': command not found
```
It is because you checked out the Nit repository with the config set to core.autocrlf true. Some git tools on Windows activate this flag by default. The git command from the Cygwin package does not that.
Heap size errors

If tools or compiled programs crash with heap size errors, you should enlarge the heap of the executable with peflag (that comes with Cygwin):
```
peflags --cygwin-heap4096 prog.exe
```