Tell cmake to use dynamic libs for Boost

conda-forge boost recipe is configured to prefer static libs for some reason.

in 1.70, the cmake files don't let you force use of dynamic libs unless BUILD_SHARED_LIBS is
set and that will cause add_library() to build libsparta as shared. ugh

Looks like this has been fixed in 1.71 (logic doesn't use BUILD_SHARED_LIBS anymore).

sparta/cmake/sparta-config.cmake

@@ -23,7 +23,16 @@ if (APPLE)
   set (CMAKE_CXX_COMPILER_VERSION 10.0)
   find_package (Boost 1.49.0 REQUIRED HINTS /usr/local/Cellar/boost/* COMPONENTS ${_BOOST_COMPONENTS})
 else ()
+  set (Boost_USE_STATIC_LIBS OFF)
+
+  # BOOST_CMAKE logic for asking for the shared libraries is broken, you can only force it to use
+  # them if you're building shared libs?  wtf?
+  set (existing_build_shared ${BUILD_SHARED_LIBS})
+  set (BUILD_SHARED_LIBS ON)
+
   find_package (Boost 1.49.0 REQUIRED COMPONENTS ${_BOOST_COMPONENTS})
+  set (BUILD_SHARED_LIBS ${existing_build_shared})
+
 endif ()
 message ("-- Using BOOST ${Boost_VERSION_STRING}")