[CB requires monolithic build normally; and that fails most of the time when that option is used; I am guessing the command line is too long.
Just for the record, Windows allows a command line length of about 8 kB.
This should be more than enough to build wxWidgets in any reasonable configuration, monolithic or not; I mean when calling the mingw make.
AFAIK, wxWidgets internally uses response files to work around the command line length limit when compiling its files.