Similar to how the configuration command line is saved in autotools' config.log, there needs to be a way to retrieve this information from Meson.
Dylan is working on this with the upstream Meson project and has plans for a stop-gap solution as well.
There is an open issue upstream for a better solution:
But in the mean time, Dylan wrote a script that does it for us.
commit 4a131a13303773d8b0e4d47e917b9c52d439146a (fdo/mr/106)
Author: Dylan Baker <email@example.com>
Date: Fri Jan 11 15:36:05 2019 -0800
meson: Add a script to extract the cmd line used for meson
Upstream I'm persuing a more comprehensive solution, but this should
prove a suitable stop-gap measure in the meantime.
The script is bin/meson-cmd-extract.py and you simply pass it the build directory, and it prints all the options back.
Marking this bug as fixed, as we have a solution for Mesa.