create shared libQZint instead of static one
---
diff -r c65c3e1348ca backend_qt/CMakeLists.txt
--- a/backend_qt/CMakeLists.txt
+++ b/backend_qt/CMakeLists.txt
@@ -12,7 +12,7 @@
     qt5_wrap_cpp(QZint_SRCS qzint.h)
 endif()
 
-add_library(${PROJECT_NAME} STATIC ${QZint_SRCS})
+add_library(${PROJECT_NAME} SHARED ${QZint_SRCS})
 
 set_target_properties(${PROJECT_NAME} PROPERTIES  SOVERSION "${ZINT_VERSION_MAJOR}.${ZINT_VERSION_MINOR}"
                                         VERSION ${ZINT_VERSION})