Adopt LuaJIT rolling release changes

[un-def]

LuaJIT recently switched to the rolling release scheme:

• 2.0.x -> 2.0.ROLLING
• 2.1.x -> 2.1.ROLLING

See LuaJIT commits:

• https://github.com/LuaJIT/LuaJIT/commit/50e0fa03c48cb9af03c3efdc3100f12687651a2e
• https://github.com/LuaJIT/LuaJIT/commit/2090842410e0ba6f81fad310a77bf5432488249a

Fixes: https://github.com/luarocks/hererocks/issues/25

---

In addition to the changing of the versioning scheme, there has been introduced some changes in the MinGW build.

See the commit and the PR:

• https://github.com/LuaJIT/LuaJIT/commit/19707009bfb8d1fe59a5c328034e8e8ad1b56232
• https://github.com/LuaJIT/LuaJIT/pull/1071

The problem is that if sh is in PATH, mingw32-make will use sh instead of cmd.exe, but some recipes in Makefile use cmd.exe syntax if MinGW is detected. I have no solid proof of it, only this post on Stack Overflow, but I did a simple experiment:

1. I have a machine with Windows and sh.exe/bash.exe provided by Git for Windows.

2. I've tried to install LuaJIT@v2.1 from the official repository (not using hererocks, only official instructions) with no success:

   D:\LuaJIT\src>mingw32-make
   VERSION   luajit.h
   /usr/bin/bash: -c: line 1: syntax error near unexpected token `('
   /usr/bin/bash: -c: line 1: `if exist ..\.git ( git show -s --format=%%ct >luajit_relver.txt ) else ( type ..\.relver >luajit_relver.txt )'
   mingw32-make: *** [Makefile:658: luajit.h] Error 2

   As you can see, bash tries to execute Windows batch script and fails (syntax error near unexpected token)

   The same with clean recipe:

   D:\LuaJIT\src>mingw32-make clean
   del luajit.exe libluajit.a lua51.dll host\minilua.exe host\buildvm.exe lj_vm.S lj_bcdef.h lj_ffdef.h lj_libdef.h lj_recdef.h lj_folddef.h host\buildvm_arch.h luajit.h luajit_relver.txt jit\vmdef.lua *.o host\*.o *.obj *.lib *.exp *.dll *.exe *.manifest *.pdb *.ilk
   /usr/bin/bash: line 1: del: command not found
   mingw32-make: *** [Makefile:626: clean] Error 127

   Yep, del instead of rm.

3. But when I either removed sh.exe from PATH or run mingw32-make with SHELL=cmd, all problem disappeared.

With this patch, we force mingw32-make to use Windows shell (SHELL=cmd).

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (7f74fc8) 79.78% compared to head (7151f5e) 68.71%.

Files	Patch %	Lines
hererocks.py	80.00%	1 Missing :warning:

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #26 +/- ## =========================================== - Coverage 79.78% 68.71% -11.08% =========================================== Files 1 1 Lines 1123 1125 +2 =========================================== - Hits 896 773 -123 - Misses 227 352 +125 ```

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[un-def]

@hishamhm Hi, you review is not mandatory, just trying to keep up to date. I am by no means an expert in C/build tools/enviroments, I am mostly a web developer, so an extra pair of eyes would be great!

[hishamhm]

@un-def yes, the change itself and the description of your experiment in the PR description LGTM!