* Fix/keep massaging git-describe result
Ref: https://github.com/neovim/neovim/pull/11117#issuecomment-536416223
* build: revisit generation of version from Git
Fixes "make clean && make", where "auto/versiondef.h" would be missing
since b18b84d - because BYPRODUCTS are apparently removed when cleaning.
This includes the following improvements/changes:
- do not run git-describe during CMake's configure phase just for
reporting
- do not print with changed Git version (too noisy, simplifies code)
* Move to src/nvim (included before config) for easier flow
* fallback to describe always, write empty include file
* update_version_stamp.lua: use prefix always
30ae60e7ca