Since commit 5a0784dd (clang-tidy: Pass by value, 2019-01-21), some of
the `RunCMake.{list,PositionIndependentCode}` cases have crashed on an
aarch64 build with GCC 6.  Avoiding use of the `std::function` move
constructor avoids the crash.  Use a strict preprocessor condition to
use this workaround only where needed.