1. I could build gstreamer using command "cerbero -c cross-android.cbc package gstreamer-1.0" and create package "gstreamer-1.0-android-arm-1.5.0" sucessfully.
2. I saw the pugin.mk in directory "share/gst-android/ndk-build", why I could not find the sink element and "souphttpsrc" element.
plugin.mk as follows:
GSTREAMER_PLUGINS_CORE := coreelements adder app audioconvert audiorate audioresample audiotestsrc gio pango typefindfunctions videoconvert videorate videoscale videotestsrc volume autodetect videofilter
GSTREAMER_PLUGINS_CAPTURE := camerabin
GSTREAMER_PLUGINS_CODECS_RESTRICTED := asfmux dtsdec faad mpegpsdemux mpegpsmux mpegtsdemux mpegtsmux voaacenc a52dec amrnb amrwbdec asf dvdsub dvdlpcmdec mad mpeg2dec xingmux realmedia x264 lame libav
GSTREAMER_PLUGINS_ENCODING := encoding
GSTREAMER_PLUGINS_CODECS_GPL := assrender
GSTREAMER_PLUGINS_NET_RESTRICTED := mms rtmp
GSTREAMER_PLUGINS_SYS := opensles opengl
GSTREAMER_PLUGINS_VIS := libvisual goom goom2k1 audiovisualizers
GSTREAMER_PLUGINS_PLAYBACK := playback
GSTREAMER_PLUGINS_EFFECTS := alpha alphacolor audiofx cairo cutter debug deinterlace dtmf effectv equalizer gdkpixbuf imagefreeze interleave level multifile replaygain shapewipe smpte spectrum videobox videocrop videomixer accurip aiff audiofxbad autoconvert bayer coloreffects debugutilsbad fieldanalysis freeverb frei0r gaudieffects geometrictransform inter interlace ivtc liveadder rawparse removesilence segmentclip smooth speed videofiltersbad audiomixer compositor
GSTREAMER_PLUGINS_CODECS := subparse ogg theora vorbis ivorbisdec alaw apetag audioparsers auparse avi dv flac flv flxdec icydemux id3demux isomp4 jpeg matroska mulaw multipart png speex taglib vpx wavenc wavpack wavparse y4menc adpcmdec adpcmenc dashdemux dvbsuboverlay dvdspu fragmented id3tag kate midi mxf openh264 opus pcapparse pnm rfbsrc schro gstsiren smoothstreaming subenc videoparsersbad y4mdec jpegformat gdp rsvg openjpeg androidmedia
GSTREAMER_PLUGINS_NET := tcp rtsp rtp rtpmanager soup udp dataurisrc sdp srtp

3. How could I create the element and link the element to a pipeline as below:
    pipeline = gst_pipeline_new("audio-player"); 
    source = gst_element_factory_make("audiotestsrc","file-source");
    decoder = gst_element_factory_make("mad","mad-decoder");
    sink = gst_element_factory_make("openslessink","audio-output");