I would have to recommend to download the source from mamedev.org (mame0145s) and not use the mame-master.zip because by the time he comes back to read the post many commits could have taken place and it would not be at a "factory" u7.
Redownload the source, mingw-mame-w32 or w64, and all 7 diffs again. I would even go as far as using a different drive for mingw and mamesrc then you should have absolutely 0 problems compiling.