Make example build optional with cmake

Author: aberaud

CMakeLists.txt

@@ -102,6 +102,7 @@ FIND_PACKAGE (Threads)
 IF (GTEST_FOUND AND ZLIB_FOUND AND THREADS_FOUND)
     OPTION (MSGPACK_BUILD_TESTS "Build msgpack tests." ON)
 ENDIF ()
+OPTION (MSGPACK_BUILD_EXAMPLES "Build msgpack examples." ON)
 
 OPTION (MSGPACK_ENABLE_CXX "Enable C++ interface." ON)
 OPTION (MSGPACK_ENABLE_SHARED "Build shared libaries in addition to static libraries." ON)
@@ -292,7 +293,9 @@ IF (NOT DEFINED CMAKE_INSTALL_LIBDIR)
     SET(CMAKE_INSTALL_LIBDIR lib)
 ENDIF ()
 
-ADD_SUBDIRECTORY (example)
+IF (MSGPACK_BUILD_EXAMPLES)
+    ADD_SUBDIRECTORY (example)
+ENDIF ()
 
 IF (MSGPACK_ENABLE_SHARED)
     SET (MSGPACK_INSTALLTARGETS msgpack msgpack-static)