This update for llvm7 and libqt5-qttools fixes the following issues:

libqt5-qttools:

- Use `libclang` instead of `clang`, now that `llvm7` moved the header files to `libclang` (bsc#1109367, bsc#1184920)

llvm7:

- Remove unneeded and unused dependencies:
  - groff, bison, flex, jsoncpp

- Devel packages are only required in other devel packages, when their headers are included in the installed headers.
- Skip a test that is broken with 387 FPU registers and avoids check failure on i586. (bsc#1145085)
- Link `libomp` with `atomic` if needed and fix build using gcc-4.8. (bsc#1145085)
- Make build of `gnustep-libobjc2` package reproducible. (bsc#1067478)
- Remove `-fno-strict-aliasing` which upstream doesn't use any more.
- Package `clang` builtin headers with `libclang`. (bsc#1109367)

  - The library is unusable without the builtin headers. Currently consumers of `libclang` have to require `clang` 
  as well, although only the headers are needed.