Add build/autotools to git ignore
Add build/autotools to git ignore

Add build/autotools to the GITIGNOREFILES variable, so that it gets added
to the generated .gitignore files.

pwithnall/mx,jonnylamb/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx