Out of curiosity, how come LibreOffice has .buckversion, BUCK, .buckconfig, etc? This commit[1] does seem to indicate using Buck to build at one point, though it is 10 years old.
[1]: https://github.com/LibreOffice/core/commit/1fd41f43eb73c373c...
[1]: https://github.com/LibreOffice/core/commit/1fd41f43eb73c373c...
Really there should be a comment in the BUCK file explaining what it is.