set Environment build root automatically - close #64

build_tests/build_dir/build_dirs_and_root.rb

@@ -1,6 +1,5 @@
 env = Rscons::Environment.new do |env|
   env.append('CPPPATH' => Rscons.glob('src/**/*/'))
   env.build_dir("src", "build")
-  env.build_root = "build_root"
   env.Program('build_dir.exe', Rscons.glob('src/**/*.c'))
 end

build_tests/build_dir/carat.rb

@@ -1,8 +1,7 @@
 Rscons::Environment.new(echo: :command) do |env|
   env.append('CPPPATH' => Rscons.glob('src/**').sort)
-  env.build_root = "build_root"
   FileUtils.mkdir_p(env.build_root)
-  FileUtils.mv("src/one/one.c", "build_root")
+  FileUtils.mv("src/one/one.c", env.build_root)
   env.Object("^/one.o", "^/one.c")
   env.Program("build_dir.exe", Rscons.glob('src/**/*.c') + ["^/one.o"])
 end

build_tests/build_dir/no_match_build_dir.rb

@@ -1,6 +1,5 @@
 Rscons::Environment.new do |env|
   env.append('CPPPATH' => Rscons.glob('src/**'))
   env.build_dir("src2", "build")
-  env.build_root = "build_root"
   env.Program('build_dir.exe', Rscons.glob('src/**/*.c'))
 end