Fails to build with Boost 1.69 (develop snapshot)

[jbeich]

After boostorg/boost#189 build fails, see error log and missing files

CMake Error at /usr/local/share/cmake/Modules/FindBoost.cmake:2049 (message):
  Unable to find the requested Boost libraries.

  Boost version: 1.69.0

  Boost include path: /usr/local/include

  Could not find the following Boost libraries:

          boost_signals

  Some (but not all) of the required Boost libraries were found.  You may
  need to install these additional Boost libraries.  Alternatively, set
  BOOST_LIBRARYDIR to the directory containing Boost libraries or BOOST_ROOT
  to the location of Boost.
Call Stack (most recent call first):
  CMakeLists.txt:41 (find_package)

Note, Boost 1.69 is scheduled to be released on 2018-12-12.

[lotem]

Thanks for the bug report.
We've been using singals2 by default. I think the bug can be fixed by not requiring the old signals library in CMake script.
Though not testing specifically against Boost 1.69, build logs show the old signals library is not involved in build any more:
https://travis-ci.org/rime/librime/jobs/447004009#L1365

[Arfrever]

Your code added in 8a9ef3b contains a typo:

if(BOOST_USE_SIGNALS2)
  add_definitions("-DBOOST_SIGNALS2")
else()
  set(BOOST_COMPONENTS ${BOOST_COMPONENTS} singals)
endif()

singals should be signals.