[clang] [llvm] [Driver][SYCL] Add initial SYCL offload compilation support (PR #117268)

[Shilei Tian via cfe-commits]

shiltian wrote:

This PR introduced a new compile warning when compiling using clang. Please fix it.

```
llvm-project/clang/lib/Driver/ToolChains/SYCL.cpp:35:10: warning: returning address of local temporary object [-Wreturn-stack-address]
   35 |   return {
      |          ^
   36 |       options::OPT_fsanitize_EQ,      // -fsanitize
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   37 |       options::OPT_fcf_protection_EQ, // -fcf-protection
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   38 |       options::OPT_fprofile_generate,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   39 |       options::OPT_fprofile_generate_EQ,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   40 |       options::OPT_fno_profile_generate, // -f[no-]profile-generate
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   41 |       options::OPT_ftest_coverage,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   42 |       options::OPT_fno_test_coverage, // -f[no-]test-coverage
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   43 |       options::OPT_fcoverage_mapping,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   44 |       options::OPT_fno_coverage_mapping, // -f[no-]coverage-mapping
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   45 |       options::OPT_coverage,             // --coverage
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   46 |       options::OPT_fprofile_instr_generate,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   47 |       options::OPT_fprofile_instr_generate_EQ,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   48 |       options::OPT_fno_profile_instr_generate, // -f[no-]profile-instr-generate
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   49 |       options::OPT_fprofile_arcs,
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   50 |       options::OPT_fno_profile_arcs, // -f[no-]profile-arcs
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from llvm-project/clang/lib/Driver/ToolChains/SYCL.cpp:8:
llvm-project/clang/lib/Driver/ToolChains/SYCL.h:27:17: warning: private field 'D' is not used [-Wunused-private-field]
   27 |   const Driver &D;
      |                 ^
2 warnings generated.
```

https://github.com/llvm/llvm-project/pull/117268