[clang] Add build option CLANG_INCLUDE_EXAMPLES (PR #187317)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve-vls` running on `linaro-g3-02` while building `clang` at step 14 "test-suite".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/143/builds/16228

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 14 (test-suite) failure: test (failure)
******************** TEST 'test-suite :: Fortran/gfortran/regression/gomp/gfortran-regression-compile-regression__gomp__imperfect2_f90.test' FAILED ********************

/home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/tools/timeit-target --timeout 7200 --limit-core 0 --limit-cpu 7200 --limit-file-size 209715200 --limit-rss-size 838860800 --redirect-input /dev/null --summary /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/Fortran/gfortran/regression/gomp/Output/gfortran-regression-compile-regression__gomp__imperfect2_f90.test.time /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/Fortran/gfortran/regression/gomp/../..//dummy
/usr/bin/diff /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/Fortran/gfortran/regression/gomp/../..//gfortran-compile-empty.reference.out /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/Fortran/gfortran/regression/gomp/gfortran-regression-compile-regression__gomp__imperfect2_f90.out
0a1,13
> error: Semantic errors in /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/test-suite/Fortran/gfortran/regression/gomp/imperfect2.f90
> /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/test-suite/Fortran/gfortran/regression/gomp/imperfect2.f90:38:9: error: This construct requires a perfect nest of depth 3, but the associated nest is a perfect nest of depth 1
>     !$omp do collapse(3) 
>           ^^
> /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/test-suite/Fortran/gfortran/regression/gomp/imperfect2.f90:43:7: because: This code prevents perfect nesting
>         call f1 (2, j)
>         ^^^^^^^^^^^^^^
> /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/test-suite/Fortran/gfortran/regression/gomp/imperfect2.f90:40:5: because: This code prevents perfect nesting
>       call f1 (1, i)
>       ^^^^^^^^^^^^^^
> /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/test-suite/Fortran/gfortran/regression/gomp/imperfect2.f90:38:12: because: COLLAPSE clause was specified with argument 3
>     !$omp do collapse(3) 
>              ^^^^^^^^^^^
\ No newline at end of file

+ /usr/bin/diff /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/Fortran/gfortran/regression/gomp/../..//gfortran-compile-empty.reference.out /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/test/sandbox/build/Fortran/gfortran/regression/gomp/gfortran-regression-compile-regression__gomp__imperfect2_f90.out

********************


```

</details>

https://github.com/llvm/llvm-project/pull/187317