Compile the FFmpeg with emcc return error

[ShawZG]

I have been troubled with compiling ffmpeg with emcc for almost a week.

First, I download the code of this project, and then ,based on the guide [http://www.briangrinstead.com/blog/] for videoconverter.js, compile return error.

shaw@ubuntu:~/share/ffmpeg$ emconfigure ./configure --prefix=../dist --cc="emcc" --disable-ffplay --disable-ffprobe --disable-ffserver --disable-asm --enable-pic

nm: /tmp/ffconf.5IUJHfaJ.o: File format not recognized
emscripten sdl2-config called with /home/shaw/tmp/myfastcomp/emscripten/emscripten/system/bin/sdl2-config --cflags
emscripten sdl2-config called with /home/shaw/tmp/myfastcomp/emscripten/emscripten/system/bin/sdl2-config --libs

install prefix ../dist
source path .
C compiler emcc
C library
ARCH c (generic)
big-endian no
runtime cpu detection yes
debug symbols yes
strip symbols yes
optimize for size no
optimizations yes
static yes
shared no
postprocessing support no
new filter support yes
network support yes
threading support pthreads
safe bitstream reader yes
SDL2 support no
opencl enabled no
JNI support no
texi2html enabled no
perl enabled yes
pod2man enabled yes
makeinfo enabled no
makeinfo supports HTML no

Enabled programs:
ffmpeg

External libraries:
iconv xlib

External libraries providing hardware acceleration:

Libraries:
avcodec avfilter avutil swscale
avdevice avformat swresample

shaw@ubuntu:~/share/ffmpeg$ emmake make

CC ffmpeg_filter.o
LD ffmpeg_g
WARNING:root:cmdutils.o is not valid LLVM bitcode
WARNING:root:ffmpeg.o is not valid LLVM bitcode
WARNING:root:emcc: cannot find library "X11"
CP ffmpeg
STRIP ffmpeg
strip:ffmpeg: File format not recognized
make: *** [ffmpeg] Error 1
ERROR:root:Configure step failed with non-zero return code 2! Command line: ['make'] at /home/shaw/share/ffmpeg

I don't konw where is wrong. Is there someone met the problem and fixed it? Thanks a lot.
PS: There is no error when I compile ffmpeg with gcc.
PPS: execute build_all_codecs.sh and build_lgpl.sh both return error.