Use "Environment" instead of "Rscons::Environment" in build tests

build_tests/library/Rsconscript

@@ -1,5 +1,5 @@
 build do
-  Rscons::Environment.new(echo: :command) do |env|
+  Environment.new(echo: :command) do |env|
     env.Program('library.exe', ['lib.a', 'three.c'])
     env.Library("lib.a", ['one.c', 'two.c'], 'CPPFLAGS' => ['-Dmake_lib'])
   end