CMake: Build lmms shared library instead of object library

Resolves some inexplicable linking errors on Windows. Saves us from
working around incomplete CMake support of object libraries.

benchmarks/CMakeLists.txt

@@ -10,6 +10,5 @@ SET(CMAKE_AUTOMOC ON)
 ADD_EXECUTABLE(benchmarks
 	EXCLUDE_FROM_ALL
 	benchmark.cpp
-	$<TARGET_OBJECTS:lmmsobjs>
 )
-TARGET_LINK_LIBRARIES(benchmarks ${QT_LIBRARIES} ${LMMS_REQUIRED_LIBS})
+TARGET_LINK_LIBRARIES(benchmarks lmmslib)