[sanitizer_common] Only use NT_GNU_BUILD_ID in sanitizer_linux_libcdep.cpp if supported

D114294 <https://reviews.llvm.org/D114294> broke the Solaris buildbots:

  /opt/llvm-buildbot/home/solaris11-amd64/clang-solaris11-amd64/llvm/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp:613:29: error: use of undeclared identifier 'NT_GNU_BUILD_ID'
          if (nhdr->n_type == NT_GNU_BUILD_ID && nhdr->n_namesz == kGnuNamesz) {
                              ^

Like D107556 <https://reviews.llvm.org/D107556>, it forgot that
`NT_GNU_BUILD_ID` is an unportable GNU extension.

Fixed by making the code conditional on the definition of the macro.

Tested on `amd64-pc-solaris2.11` and `sparcv9-sun-solaris2.11`.

Differential Revision: https://reviews.llvm.org/D117051