When testing Boost 1.68 in
DM-15385, afw fails to build almost immediately because of failures in lsstGil.h.
In v1.68 GIL_DEFINE_BASE_TYPEDEFS gains a new argument in the middle:
This is not documented as a breaking change so I wonder if we are using internal APIs here. The immediate fix would be to add the channel model definition to our header file, but it would be preferable to use a public API if one exists since that might also work for boost 1.66 (that we are currently using).