With wxWidgets 2.9.2 now in Externals, SCons was the only
external dependency other than Xcode and building just SCons
from Macports caused a fair mount of extra stuff to be built
unnecessarily, so just include a copy of scons-local.
Always build wxWidgets from Externals which allows us to get
rid of the home-grown autoconf machinery in SconsTests.
The main use case for args.cache was the wxconfig option,
which is no longer relevant after the above changes and
caching options has a lot of potential for confusion,
especially since other build systems don't tend to do this,
so we no longer do it now.
git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@7381 8ced0084-cf51-0410-be5f-012b33b47a6e
