fix gr and add mingw-w64 (#355)

* fix gr

* add mingw-w64

* remove unused path

packages/g/gr/xmake.lua

@@ -56,7 +56,10 @@ package("gr")
 
     on_install("windows|x64", "macosx", "linux|x86,x86_64", function (package)
         os.cp("*", package:installdir())
+        package:addenv("PATH", ".")
         package:addenv("PATH", "bin")
+        package:addenv("GRDIR", package:installdir())
+        package:addenv("GKS_WSTYPE", package:is_plat("windows") and "41" or "x11")
     end)
 
     on_test(function (package)

packages/m/mingw-w64/xmake.lua

@@ -0,0 +1,40 @@
+package("mingw-w64")
+
+    set_kind("toolchain")
+    set_homepage("https://sourceforge.net/projects/mingw-w64/")
+    set_description("The mingw-w64 project is a complete runtime environment for gcc to support binaries native to Windows 64-bit and 32-bit operating systems.")
+
+    if is_arch("x86") then
+        add_urls("https://jaist.dl.sourceforge.net/project/mingw-w64/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/$(version)/threads-posix/sjlj/i686-$(version)-release-posix-sjlj-rt_v6-rev0.7z")
+        add_versions("8.1.0", "f5b97d1a8c15f527c0f0397d0f128ff0af6acc9fab1ecd79ad403661c0a425ac")
+    else
+        add_urls("https://jaist.dl.sourceforge.net/project/mingw-w64/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/$(version)/threads-posix/seh/x86_64-$(version)-release-posix-seh-rt_v6-rev0.7z")
+        add_versions("8.1.0", "853970527b5de4a55ec8ca4d3fd732c00ae1c69974cc930c82604396d43e79f8")
+    end
+
+    add_configs("python2", {description = "Export builtin python2.", default = false, type = "boolean"})
+
+    on_fetch("@windows", function (package, opt)
+        if opt.system then
+            local mingw = import("detect.sdks.find_mingw")()
+            if mingw then
+                package:addenv("PATH", mingw.bindir)
+                return true
+            end
+        end
+    end)
+
+    on_install("@windows", function (package)
+        os.cp("*", package:installdir())
+        if package:config("python2") then
+            package:addenv("PATH", path.join("opt", "bin"))
+        end
+    end)
+
+    on_test(function (package)
+        os.vrun("gcc -v")
+        os.vrun("gfortran -v")
+        if package:config("python2") then
+            os.vrun("python2 --version")
+        end
+    end)