Change isn't bogus, with this commit building subpackage gives :
[00:00:02] Warning: (graphics/mesa-libs): Error: graphics/mesa-libs has dependency on graphics/libdrm with invalid empty FLAVOR; Please contact maintainer of the port to fix this.
[00:00:02] Warning: (graphics/mesa-libs): Error: graphics/mesa-libs has dependency on graphics/libdrm with invalid empty FLAVOR; Please contact maintainer of the port to fix this.
[00:00:02] Warning: (graphics/mesa-libs): Error: graphics/mesa-libs has dependency on graphics/libdrm with invalid empty FLAVOR; Please contact maintainer of the port to fix this.
https://github.com/freebsd/poudriere/commit/095b50c360060209604731fe5d015920a9cefe73
@evadot