Ceph » rgw

https://github.com/ceph/ceph/pull/14273 introduces a regression in that it breaks the s390x build.

The immediate cause of the build failure is this line: https://github.com/ceph/ceph/blob/5b41fb55e40833de55e1d93e0be07c6da319a8bb/CMakeLists.txt#L511

I.e. the introduction of "context" as a required Boost component.

The build fails on find_package(Boost . . .) with the following message:

[  228s] CMake Error at /usr/share/cmake/Modules/FindBoost.cmake:1657 (message):
[  228s]   Unable to find the requested Boost libraries.
[  228s] 
[  228s]   Boost version: 1.63.0
[  228s] 
[  228s]   Boost include path:
[  228s]   /home/abuild/rpmbuild/BUILD/ceph-12.0.3+git.1495491843.99463ac8f3/build/boost/include
[  228s] 
[  228s] 
[  228s]   Could not find the following static Boost libraries:
[  228s] 
[  228s]           boost_context
[  228s] 
[  228s]   Some (but not all) of the required Boost libraries were found.  You may
[  228s]   need to install these additional Boost libraries.  Alternatively, set
[  228s]   BOOST_LIBRARYDIR to the directory containing Boost libraries or BOOST_ROOT
[  228s]   to the location of Boost.
[  228s] Call Stack (most recent call first):
[  228s]   CMakeLists.txt:595 (find_package)