Make bintest enabling like other `enable_xxx` methods.

build_config.rb

@@ -80,7 +80,7 @@ MRuby::Build.new do |conf|
   # conf.file_separator = '/'
 
   # bintest
-  # conf.enable_bintest = true
+  # conf.enable_bintest
 end
 
 # Define cross build settings

doc/compile/README.md

@@ -193,7 +193,7 @@ If you want a temporary files use `tempfile` module of CRuby instead of ```/tmp/
 
 You can enable it with following:
 
-	conf.enable_bintest = true
+	conf.enable_bintest
 
 ### C++ ABI
 

tasks/mruby_build.rake

@@ -43,8 +43,9 @@ module MRuby
     end
     include Rake::DSL
     include LoadGems
-    attr_accessor :name, :bins, :exts, :file_separator, :build_dir, :gem_clone_dir, :enable_bintest
+    attr_accessor :name, :bins, :exts, :file_separator, :build_dir, :gem_clone_dir
     attr_reader :libmruby, :gems
+    attr_writer :enable_bintest
 
     COMPILERS = %w(cc cxx objc asm)
     COMMANDS = COMPILERS + %w(linker archiver yacc gperf git exts mrbc)
@@ -111,6 +112,14 @@ module MRuby
       @cxx_abi_enabled = true
     end
 
+    def enable_bintest
+      @enable_bintest = true
+    end
+
+    def bintest_enabled?
+      @enable_bintest
+    end
+
     def toolchain(name)
       tc = Toolchain.toolchains[name.to_s]
       fail "Unknown #{name} toolchain" unless tc

travis_config.rb

@@ -19,7 +19,7 @@ MRuby::Build.new do |conf|
   conf.compilers.each do |c|
     c.defines += %w(MRB_DEBUG MRB_GC_FIXED_ARENA)
   end
-  conf.enable_bintest = true
+  conf.enable_bintest
 end
 
 MRuby::Build.new('cxx_abi') do |conf|
@@ -30,7 +30,7 @@ MRuby::Build.new('cxx_abi') do |conf|
   conf.compilers.each do |c|
     c.defines += %w(MRB_DEBUG MRB_GC_FIXED_ARENA)
   end
-  conf.enable_bintest = true
+  conf.enable_bintest
 
   enable_cxx_abi
 end