[Flang][OpenMP] Fix to resolve the crash with SIMD aligned clause. (#150612)

**Issue:**
When SIMD aligned clause has a alignment value which is not a power of
2, compiler crashes with error Assertion (alignment & (alignment - 1))
== 0 && "alignment is not power of 2"

**Fix:**
According to LLVM Language Reference manual
[[link]](https://llvm.org/docs/LangRef.html#assume-opbundles), the
alignment value may be non-power-of-two. In that case, the pointer value
must be a null pointer otherwise the behavior is undefined.

So instead of emitting `llvm.assume` intrinsic function with a null
pointer having the specified alignment, modified the implementation
which ignores the aligned clause which has an alignment value which is
not a power of 2. This patch also emits a warning indicating that the aligned clause is ignored if the alignment value is not a power of two.

It fixes the issue https://github.com/llvm/llvm-project/issues/149458
6 files changed
tree: ef5d623e5748487e301e4ab82754404aa52ff1f7
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libsycl/
  16. libunwind/
  17. lld/
  18. lldb/
  19. llvm/
  20. llvm-libgcc/
  21. mlir/
  22. offload/
  23. openmp/
  24. orc-rt/
  25. polly/
  26. runtimes/
  27. third-party/
  28. utils/
  29. .clang-format
  30. .clang-format-ignore
  31. .clang-tidy
  32. .git-blame-ignore-revs
  33. .gitattributes
  34. .gitignore
  35. .mailmap
  36. CODE_OF_CONDUCT.md
  37. CONTRIBUTING.md
  38. LICENSE.TXT
  39. pyproject.toml
  40. README.md
  41. SECURITY.md
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