The problem is that NDK build system strips all prebuilt shared libraries when copying them to destination folder.
If you really need to use a libjpeg as shared library, then I would suggest that you run a post build script to copy the original file to the destination folder overwriting the stripped one.
The best solution is to prebuild a libjpeg.a static library and then you can avoid stripping like this:
include $(CLEAR_VARS)
LOCAL_MODULE := libjpeg
LOCAL_SRC_FILES :=../lib1/libjpeg.a
include $(PREBUILT_STATIC_LIBRARY)
...
include $(CLEAR_VARS)
LOCAL_MODULE := mylib
LOCAL_SRC_FILES := mylib.cpp
LOCAL_C_INCLUDES := $(LOCAL_PATH)/../lib1/include/
LOCAL_WHOLE_STATIC_LIBRARIES := libjpeg
...
include $(BUILD_SHARED_LIBRARY)
Notice the LOCAL_WHOLE_STATIC_LIBRARIES which turns off the stripping for these libs.