Surprisingly, after this "make depend && make" recompiles EveryThing in my tree. I dont understand why, almost no program relies on twain_32.dll.so, so could someone shed some light here ?
because it changed the include/config.h file, which contains all configuration specific information (libraries you have or you don't...). Since config.h is quite heavily included in Wine source, it implied the whole recompilation.
HTH A+