Install flib_dpb library and remove uneeded target dependency

On some systems the library seems to be needed in the installation. See !1005 (closed).

The dependency is not needed. Neither the library nor the header files are used.

Both changes solve the same problem.

external/flib_dpb/CMakeLists.txt

@@ -10,4 +10,6 @@ set(LIB_HEADERS flib_dpb/MicrosliceContents.hpp)
 
 add_Library(flib_dpb SHARED ${LIB_SOURCES} ${LIB_HEADERS})
 target_include_directories(flib_dpb PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/flib_dpb)
-Set_Target_Properties(flib_dpb PROPERTIES  SUFFIX ".so")
+
+install(TARGETS flib_dpb DESTINATION lib)
+install(FILES ${LIB_HEADERS} DESTINATION include)