Command, I Used, to build wxWidgets 2.9.0 RC2
http://biolpc22.york.ac.uk/pub/2.9.0-rc2/Still Testing These Options, but should work.
While working on Patches to Source Code will be using wxUSE_STC=0 and USE_STC=0 to avoid Build Errors because of two wxscintilla libs.
mingw32-make -f makefile.gcc USE_PROPGRID=1 USE_OPENGL=0 USE_XRC=1 SHARED=1 MONOLITHIC=1 BUILD=release UNICODE=1 CPPFLAGS="-Wmissing-include-dirs"
Optional: CPPFLAGS="-Wmissing-include-dirs"
Required: CXXFLAGS="-fno-strict-aliasing" Not Certain: LDFLAGS="-enable-stdcall-fixup"Required for wxSmith: USE_PROPGRID=1
Patch to Code::Blocks needed if NOT wxUSE_STC=0 and USE_STC=0
Edit: Changed Patch to see if this one works better, than last one.
Patch Fails to work too often to be maintained.