Update to rscons-3.1.0

Rsconscript

@@ -7,8 +7,7 @@ configure do
   check_lib "freeimage"
 end
 
-build do
-  Environment.new do |env|
+env do |env|
   env["CCFLAGS"] += %w[-Wall -O2]
   env["CPPPATH"] += glob("src/**")
 
@@ -19,5 +18,4 @@ build do
   sources = glob("src/**/*.cc")
   sources += ["^/parser/lexer.cc", "^/parser/parser.cc"]
   env.Program("fart", sources)
-  end
 end