Fix error found building relocation packer for host bionic

bionic/tools/relocation_packer/src/main.cc:109:7: error: comparison of constant
-1 with expression of type 'typeof (read(fd.get(), e_ident, (16)) != (16))'
(aka 'bool') is always false [-Werror,-Wtautological-constant-out-of-range-compare]

  if (TEMP_FAILURE_RETRY(read(fd.get(), e_ident, EI_NIDENT) != EI_NIDENT)) {
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

bionic/libc/include/unistd.h:243:18: note: expanded from macro 'TEMP_FAILURE_RETRY'
    } while (_rc == -1 && errno == EINTR); \
             ~~~ ^  ~~
1 error generated.

Bug: 31559095
Test: mmma bionic
Change-Id: I473a19e3d51ff355233ae7f87b1013be069edb1f