Fix dynamic linking Boost on Arch Linux (#6697)

Fix dynamic linking Boost

Signed-off-by: Filipe Laíns <lains@riseup.net>
Co-authored-by: SoftFever <softfeverever@gmail.com>

CMakeLists.txt

@@ -411,6 +411,8 @@ if(SLIC3R_STATIC)
     set(Boost_USE_STATIC_LIBS ON)
     # Use boost libraries linked statically to the C++ runtime.
     # set(Boost_USE_STATIC_RUNTIME ON)
+else()
+    add_definitions(-DBOOST_LOG_DYN_LINK)
 endif()
 #set(Boost_DEBUG ON)
 # set(Boost_COMPILER "-mgw81")