I managed to work around that for Emscripten 1.38.5 by adding an
explicit definition of noexcept Player::Track copy
constructor/assignment, but that didn't solve anything for Emscripten,
iOS or Android. Since I can't reproduce that on *anything* I have on
this machine and it seems that the problem somehow just goes away when
using a more recent Clang, I decided to just remove the noexcept
specifier altogether.
I had a temptation to make it noexcept everywhere except Clang, but that
might add potential portability issues (code that works with GCC would
suddenly break on Clang without any clear reason).