man vim, "FILES:" section
System wide Vim initializations.
but it seems that file is not used anymore (maybe the same is true for
/usr/share/vim/gvimrc but I can't test it), in fact:
says something different:
system vimrc file: "/usr/share/vim/vim57/macros/vimrc"
system vimrc file: "$VIM/vimrc"
and on my system it refers to /usr/share/vim/vimrc
I've fixed the man page in 5.7-4.
We've decided to move vimrc to the version-specific directory because vim 6.0
needs slightly different options than 5.7.