scons,sim: Eliminate the generated cxx_config/init.cc file.

This file populated the "cxx_config_directory" map from type names to
directory entry generating types. It used a comprehensive list of
includes of all SimObject headers, and a comprehensive list of the
generating types to fill everything in.

Instead, this change creates a new singleton helper class which, when
instantiated as a static member of a CxxConfigParams subclass, will
install a pointer to a CxxConfigDirectoryEntry to that map during global
object construction time.

Also, this change renames the map to cxxConfigDirectory which is in
compliance with the style guide, and puts it behind an accessor which
returns a static variable which is the actual map. This avoids any
problems that might come from global object construction order.

Change-Id: Iaa913fbe5af1b11d90ca618e29420eeb7cb0faed
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49455
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
6 files changed