add wasm ffmpeg build script

scripts/build_wasm_ffmpeg.sh

@@ -0,0 +1,96 @@
+#!/bin/bash
+# set -exuo pipefail
+OS=$(uname)
+INSTALL_DIR=$(pwd)/ffmpeg
+if [ ${OS} != "Linux" ]
+then
+    echo "Not support other platform yet".
+    exit
+fi
+
+function build_x264() {
+    cd $1
+    git clone https://code.videolan.org/videolan/x264.git
+    cd x264
+    CONF_FLAGS=(
+        --prefix=$INSTALL_DIR           # lib installation dir
+        --host=x86-gnu                  # use x86 linux host
+        --enable-static                 # build static library
+        --disable-cli                   # disable cli build
+        --disable-asm                   # disable assembly
+        --disable-thread
+        --extra-cflags="-fPIC -pthread"
+    )
+    emconfigure ./configure "${CONF_FLAGS[@]}"
+    emmake make install-lib-static -j
+}
+
+function build_x265() {
+    cd $1
+    # x265 needs some edits. 
+    # Should we use a personal repo?
+    git clone --branch stable --depth 7 https://github.com/ruiqurm/x265
+    cd source
+    mkdir build
+    cd build
+    CONF_FLAGS=(
+        -DCMAKE_INSTALL_PREFIX=$INSTALL_DIR
+        -DENABLE_LIBNUMA=OFF
+        -DENABLE_SHARED=OFF
+        -DENABLE_CLI=OFF
+        -DCMAKE_CXX_FLAGS="-msimd128"
+        -DCMAKE_C_FLAGS="-msimd128"
+    )
+    emmake cmake .. ${CONF_FLAGS[@]}
+    mmake make -j
+    emmake make install -j
+}
+
+function build_ffmpeg() {
+    cd $1
+    curl -O -L https://ffmpeg.org/releases/ffmpeg-4.4.tar.bz2
+    tar xjvf ffmpeg-4.4.tar.bz2
+    cd ffmpeg-4.4
+    export CFLAGS="-I$INSTALL_DIR/include $CFLAGS"
+    export CXXFLAGS="$CFLAGS"
+    export LDFLAGS="-L$INSTALL_DIR/lib $LDFLAGS $CFLAGS"
+    export EM_PKG_CONFIG_PATH=$EM_PKG_CONFIG_PATH:$INSTALL_DIR/lib/pkgconfig:$EMSDK/upstream/emscripten/system/lib/pkgconfig
+    export EM_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake
+    export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$EM_PKG_CONFIG_PATH
+    CONF_FLAGS=(
+        --prefix=$INSTALL_DIR         # lib installation dir
+        --target-os=none              # disable target specific configs
+        --arch=x86_32                 # use x86_32 arch
+        --disable-pthreads
+        --disable-os2threads
+        --disable-w32threads
+        --enable-libx264
+        --enable-gpl
+        --enable-cross-compile        # use cross compile configs
+        --disable-asm                 # disable asm
+        --disable-stripping           # disable stripping as it won't work
+        --disable-programs            # disable ffmpeg, ffprobe and ffplay build
+        --disable-doc                 # disable doc build
+        --disable-debug               # disable debug mode
+        --disable-runtime-cpudetect   # disable cpu detection
+        --disable-autodetect          # disable env auto detect
+        --nm=emnm
+        --ar=emar
+        --ranlib=emranlib
+        --cc=emcc
+        --cxx=em++
+        --objcc=emcc
+        --dep-cc=emcc
+        --extra-cflags="-fPIC -pthread"
+    )
+    emconfigure ./configure "${CONF_FLAGS[@]}"
+    emmake make -j
+    emmake make install
+}
+
+
+
+BUILD_PATH=$(pwd)/ffmpeg/build
+mkdir -p $BUILD_PATH
+build_x264 $BUILD_PATH
+build_ffmpeg $BUILD_PATH