Add status for BPF skeletons, to see if a build has them enabled:
```
$ perf version --build-options
perf version 6.6.rc1.g0381ae36d1a6
                 dwarf: [ OFF ]  # HAVE_DWARF_SUPPORT
    dwarf_getlocations: [ OFF ]  # HAVE_DWARF_GETLOCATIONS_SUPPORT
         syscall_table: [ on  ]  # HAVE_SYSCALL_TABLE_SUPPORT
                libbfd: [ OFF ]  # HAVE_LIBBFD_SUPPORT
            debuginfod: [ OFF ]  # HAVE_DEBUGINFOD_SUPPORT
                libelf: [ OFF ]  # HAVE_LIBELF_SUPPORT
               libnuma: [ OFF ]  # HAVE_LIBNUMA_SUPPORT
numa_num_possible_cpus: [ OFF ]  # HAVE_LIBNUMA_SUPPORT
               libperl: [ on  ]  # HAVE_LIBPERL_SUPPORT
             libpython: [ on  ]  # HAVE_LIBPYTHON_SUPPORT
              libslang: [ on  ]  # HAVE_SLANG_SUPPORT
             libcrypto: [ on  ]  # HAVE_LIBCRYPTO_SUPPORT
             libunwind: [ OFF ]  # HAVE_LIBUNWIND_SUPPORT
    libdw-dwarf-unwind: [ OFF ]  # HAVE_DWARF_SUPPORT
                  zlib: [ on  ]  # HAVE_ZLIB_SUPPORT
                  lzma: [ on  ]  # HAVE_LZMA_SUPPORT
             get_cpuid: [ on  ]  # HAVE_AUXTRACE_SUPPORT
                   bpf: [ OFF ]  # HAVE_LIBBPF_SUPPORT
                   aio: [ on  ]  # HAVE_AIO_SUPPORT
                  zstd: [ on  ]  # HAVE_ZSTD_SUPPORT
               libpfm4: [ on  ]  # HAVE_LIBPFM
         libtraceevent: [ on  ]  # HAVE_LIBTRACEEVENT
         bpf_skeletons: [ OFF ]  # HAVE_BPF_SKEL
```
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Namhyung Kim <namhyung@kernel.org>
Cc: James Clark <james.clark@arm.com>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Patrice Duroux <patrice.duroux@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Tom Rix <trix@redhat.com>
Cc: llvm@lists.linux.dev
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230914211948.814999-2-irogers@google.comSigned-off-by: Namhyung Kim <namhyung@kernel.org>