Merge pull request #1592 from perlun/auto-toolchain

Automatically detect toolchain if it is visualcpp, and hence we drop vs2010.rake altogether - it’s no longer needed.

build_config.rb

 MRuby::Build.new do |conf|
   # load specific toolchain settings
-  toolchain :gcc
+
+  # Gets set by the VS command prompts.
+  if ENV['VisualStudioVersion']
+    toolchain :visualcpp
+  else
+    toolchain :gcc
+  end
 
   # Use mrbgems
   # conf.gem 'examples/mrbgems/ruby_extension_example'

tasks/toolchains/vs2012.rake → tasks/toolchains/visualcpp.rake

-MRuby::Toolchain.new(:vs2012) do |conf|
+MRuby::Toolchain.new(:visualcpp) do |conf|
   [conf.cc, conf.cxx].each do |cc|
     cc.command = ENV['CC'] || 'cl.exe'
     cc.flags = [ENV['CFLAGS'] || %w(/c /nologo /W3 /D_DEBUG /MDd /Zi /Od /RTC1 /DHAVE_STRING_H /DNO_GETTIMEOFDAY /D_CRT_SECURE_NO_WARNINGS)]

tasks/toolchains/vs2010.rake

-MRuby::Toolchain.new(:vs2010) do |conf|
-  toolchain :vs2012
-end