The GCC 5.4.0 rebuilds are now completed & tested on several internal ISOs.
All has now moved to the stable repositories. This move was for nearly 1100 packages, so expect that the biggest part of your install will be replaced on your next update.

Among the things that have changed:

  • A gcc 5.4.0 & binutils 2.26.1 based new toolchain, cloog no longer needed, isl build into gcc
  • kernel moved to linux 4.6.4
  • full rebuild of the [core] repository
  • complete rebuild of the entire X-stack & sound-stack
  • all Qt5 packages rebuild
  • Plasma 5.7.1
  • KDE Applications 16.04.3
  • llvm/clang updated to 3.8.1, added lldb 3.8.1
  • GIMP moved to new major 2.9 series, available as 2.9.4
  • virtualbox Qt5 based moved to stable 5.1 release

DO NOT update until you are sure your mirrors have synced.
Use

upd

to update, do not proceed if it shows your mirror has not synced, or run:

mirror-check

And as always, starting Octopi will show you if your mirror has synced.
If not synced, wait a few hours and try again.