build failure due to undefined symbol with gcc 7.3.1

release-external-32 is failing to build on Fedora 27 with gcc 7.3.1: http://dynamorio.org/CDash/buildSummary.php?buildid=35315

CMake Error at /work/dr/nightly/src/core/CMake_readelf.cmake:94 (message):
  *** Error:
  /.../build_release-external-32/lib32/release/libdynamorio.so
  has undefined symbol: GLOBAL DEFAULT UND __divdi3