sim,misc: Move protobuf housekeeping out of gem5Main.

Put that code into a singleton class in src/proto, so that it gets
called during initialization and teardown of gem5 without cluttering up
gem5Main. This also removes the need to use #ifdefs to guard for
actualling having protobuf support.

Change-Id: I93b5d994eee478a9c159a3f3d02b3e996af02a3e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49416
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/init.cc

@@ -53,14 +53,8 @@
 #include "base/cprintf.hh"
 #include "base/logging.hh"
 #include "base/types.hh"
-#include "config/have_protobuf.hh"
 #include "python/pybind11/pybind.hh"
 
-#if HAVE_PROTOBUF
-#include <google/protobuf/stubs/common.h>
-
-#endif
-
 namespace py = pybind11;
 
 namespace gem5
@@ -204,14 +198,6 @@ PYBIND11_EMBEDDED_MODULE(_m5, _m5)
 int
 gem5Main(int argc, char **argv)
 {
-#if HAVE_PROTOBUF
-    // Verify that the version of the protobuf library that we linked
-    // against is compatible with the version of the headers we
-    // compiled against.
-    GOOGLE_PROTOBUF_VERIFY_VERSION;
-#endif
-
-
     // Embedded python doesn't set up sys.argv, so we'll do that ourselves.
     py::list py_argv;
     auto sys = py::module::import("sys");
@@ -239,10 +225,6 @@ gem5Main(int argc, char **argv)
         return 1;
     }
 
-#if HAVE_PROTOBUF
-    google::protobuf::ShutdownProtobufLibrary();
-#endif
-
     return 0;
 }