Req: Hide build folder under MS Windows

[btoschek]

With the current setup, the .build directory is visible by default under MS Windows. To mimic Linux behavior, this directory should imo be hidden automatically during its creation. This can be done (as far as I've seen) by including the following line into the relevant section in the Makefile:

attrib +h $(BUILD_DIR)

Whilst I need someone to test the suggested change for me, it should also be discussed if this is desired behavior for Windows users. As a side-note, the folder can always be brought back into view with the opt-in setting of "Show hidden files" in the file browser.