Bump llvm-project from 08bb427 to 2015abf

Bumps [llvm-project](https://github.com/Xilinx/llvm-project) from `08bb427` to `2015abf`.
- [Commits](Xilinx/llvm-project@08bb427...2015abf)

---
updated-dependencies:
- dependency-name: llvm-project
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>