scons: Add sim_object and enums arguments to SimObject().

This will explicitly declare what SimObject and Enum types need to be set
up in C++, which will make importing all the SimObject modules during
the setup phase of SCons uneccessary.

Change-Id: Id2d7603daf33b236ceaa0789e2f089f589d34e62
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49406
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/cpu/trace/SConscript

@@ -5,7 +5,7 @@ if env['TARGET_ISA'] == 'null':
 
 # Only build TraceCPU if we have support for protobuf as TraceCPU relies on it
 if env['HAVE_PROTOBUF']:
-    SimObject('TraceCPU.py')
+    SimObject('TraceCPU.py', sim_objects=['TraceCPU'])
     Source('trace_cpu.cc')
 
 DebugFlag('TraceCPUData')