With the adoption of
RFC-398 the road is open to using Anaconda 5.0 and devtoolset-6, which in turn enables C++14 support.
However, because Anaconda 5.0 is compiled with a newer GCC (7.2.0) then even devtoolset-6 provides (GCC 6.3.1), LTO is broken (lto bytecode stream generated by GCC 7.2.0 can't be used by GCC 6.3.1).
This problem has been reported to Anaconda upstream (#6619), but I don't think they can change much about it without going to older compilers.
So instead, turning off LTO in our build (with -fno-lto) works around this problem.
This RFC proposes to add this option to sconsUtils (for GCC only) until devtoolset-7 is released and we can use that (after a separate RFC) instead.
I expect the benefits from LTO to be small, and outweighed by the performance increase from using more modern compilers.