On April 7, LLVM10 was checked in to openSUSE:Factory - this results in
duplicate binaries being created, which is a major problem, as there is no
control which of the two is being available in the repo and for further product
builds..

e.g. mozjs68 is unresolvable with: nothing provides clang-tools = 9.0.1 needed
by clang9-devel, (got version 10.0.0-1.1) (llvm10 was last built, winning this
time inside OBS; for the repo it could be different)

Duplicate binaries found:
x86_64:
  clang-tools:
  - llvm10
  - llvm9
  libc++-devel:
  - llvm10
  - llvm9
  libc++1:
  - llvm10
  - llvm9
  libc++abi-devel:
  - llvm10
  - llvm9
  libc++abi1:
  - llvm10
  - llvm9
  python3-clang:
  - llvm10
  - llvm9

For the time being, I revert the addition of LLVM10 to Tumbleweed (no snapshot
broken yet)