Missing package in the FAQ doc

[Orgad Shaneh]

Hi,

On How do I build Cygwin on my own[1], there is a list of packages
that are required for building cygwin.

The "patch" package should be added to the list.

And I also needed to install cocom for shilka. Had this error:
../../../../winsup/cygwin/gendevices
../../../../winsup/cygwin/devices.in
../../../../winsup/cygwin/devices.cc
../../../../winsup/cygwin/gendevices: shilka command missing? - No
such file or directory
make[4]: *** [Makefile:2889: ../../../../winsup/cygwin/devices.cc] Error 2

According to the FAQ, it is only required "If you change a certain
core part of Cygwin, namely the layout of the Cygwin TLS area".

And last thing - I didn't install xmlto and the other doc tools, and
make failed.

So either configure should check for their existence and not build doc
if they don't exist, or at least suggest running make -k if these
tools are not installed.

Thanks.

[1] https://cygwin.com/faq.html#faq.programming.building-cygwin