Some fixes.

interpreter.py

@@ -149,7 +149,7 @@ class Interpreter():
                 raise InvalidArguments('Line %d: Argument %s is not a string.' % str(a))
         name = args[0]
         sources = args[1:]
-        if name in self.target:
+        if name in self.targets:
             raise InvalidCode('Line %d, tried to create executable "%s", but a build target of that name already exists.' % (node.lineno(), name))
         exe = Executable(name, sources)
         self.targets[name] = exe

shellgenerator.py

@@ -98,6 +98,6 @@ if __name__ == '__main__':
     import interpreter, environment
     os.chdir(os.path.split(__file__)[0])
     envir = environment.Environment('.', 'work area')
-    intpr = interpreter.Interpreter(code)
+    intpr = interpreter.Interpreter(code, envir.get_scratch_dir())
     g = ShellGenerator(intpr, envir)
     g.generate()