BUILD: Build fails with doxygen issues on AArch64 ubuntu 18.04

Created by: joshua-warburton

Building dynamorio fails during documentation generation on AArch64 ubuntu 18.04 with the following error

CMake Error at ./dynamorio/api/docs/CMake_rundoxygen.cmake:154 (message):
  *** /usr/bin/doxygen failed: ***

  ./dynamorio-build/include/dr_tools.h:2691: warning:
  expected whitespace after [ command

  ./dynamorio-build/include/dr_tools.h:2667: warning:
  expected whitespace after [ command

  ./dynamorio-build/include/dr_tools.h:2635: warning:
  expected whitespace after [ command

  ./dynamorio-build/include/dr_tools.h:2657: warning:
  expected whitespace after [ command

  ./dynamorio-build/include/dr_tools.h:2677: warning:
  expected whitespace after [ command

  ./dynamorio-build/include/dr_tools.h:2703: warning:
  expected whitespace after [ command



api/docs/CMakeFiles/htmldocs.dir/build.make:488: recipe for target 'api/docs/html/index.html' failed

This is with the default version of doxygen, 1.8.3.

If doxygen is updated to the latest version, we get instead:

CMake Error at ./dynamorio/api/docs/CMake_doxyfile.cmake:188 (message):
  /usr/local/bin/doxygen -u failed: This tag has been removed.