gpac for android

作者在编译extra_libs的ffmpeg部分时遇到了编译错误，目前还未成功编译（暂时搁置了）。

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1 首先编译gpac外部依赖库

Get extra_libs source code from here. Then, goto /build/android and run the script:

./gpac_build_all_extra_libs <Android_NDK_DIR>

ps：<Android_NDK_DIR>指的是ndk的路径

报错1：

arm-linux-androideabi-4.9prebuiltwindows-x86_64/bin/arm-linux-androideabi-gcc is unable to create an executable file.
C compiler test failed.

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
Include the log file "config.log" produced by configure as this will help
solve the problem.

解决1:
compile_ffmpeg_android.sh中增加export TMPDIR=D:/cgywin/tmp

报错2：

cannot open crtbegin_dynamic.o: No such file or directory
cannot open crtend_android.o: No such file or directory
error: cannot find -lc
error: cannot find -ldl

解决2：

将android-ndk-r10e\platforms\android-9\arch-arm\usr\lib下的所有文件copy到android-ndk-r10e\toolchains\arm-linux-androideabi-4.9\prebuilt\windows-x86_64\lib\gcc\arm-linux-androideabi\4.9下

如果编译成功后将extra_libs放入gpac的extra_lib目录下。

2 编译gpac

执行configure，然后make，最后应该是在bin目录下生成编译好的.a。