• The original

• The original guide is here Cross compile WebRTC for Raspberry Pi

• Building a Raspberry Pi 2 WebRTC camera

• The environment

You know, Linux distributions are conflict. Even Ubuntu(Especially Ubuntu), version to version may result in building complex software Success or Fail. Here are the validated distributions:

    lsb_release -a

    No LSB modules are available.
    Distributor ID:	Ubuntu
    Description:	Ubuntu 15.04
    Release:	15.04
    Codename:	vivid

or

   lsb_release -a

   LSB Version:	:core-4.1-amd64:core-4.1-noarch:cxx-4.1-amd64:cxx-4.1-noarch:desktop-4.1-amd64:desktop-4.1-noarch:languages-4.1-amd64:languages-4.1-noarch:printing-4.1-amd64:printing-4.1-noarch
   Distributor ID:	CentOS
   Description:	CentOS Linux release 7.1.1503 (Core) 
   Release:	7.1.1503
   Codename:	Core

• Install Toolchain : *3

   sudo git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git /opt/depot_tools
   echo "export PATH=/opt/depot_tools:\$PATH" | sudo tee /etc/profile.d/depot_tools.sh
  
   sudo git clone https://github.com/raspberrypi/tools.git /opt/rpi_tools
  
   echo "export PATH=/opt/rpi_tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin:\$PATH" | sudo tee /etc/profile.d/rpi_tools.sh
   source /etc/profile
  

• Build sysroot : *2

   sudo apt-get install qemu-user-static debootstrap
   sudo debootstrap --arch armhf --foreign --include=g++,libasound2-dev,libpulse-dev,libudev-dev,libexpat1-dev,libnss3-dev,libgtk2.0-dev wheezy rootfs
   sudo cp /usr/bin/qemu-arm-static rootfs/usr/bin/
   sudo chroot rootfs /debootstrap/debootstrap --second-stage
   find rootfs/usr/lib/arm-linux-gnueabihf -lname '/*' -printf '%p %l\n' | while read link target
   do
       sudo ln -snfv "../../..${target}" "${link}"
   done
   find rootfs/usr/lib/arm-linux-gnueabihf/pkgconfig -printf "%f\n" | while read target 
   do
       sudo ln -snfv "../../lib/arm-linux-gnueabihf/pkgconfig/${target}" rootfs/usr/share/pkgconfig/${target}
   done
  

• Build : *1

   export GYP_CROSSCOMPILE=1
   export GYP_DEFINES="target_arch=arm arm_float_abi=hard clang=1 include_tests=0 sysroot=$(pwd)/rootfs werror="
   export GYP_GENERATOR_OUTPUT='arm'
  
   fetch --no-history webrtc
   ninja -C src/$GYP_GENERATOR_OUTPUT/out/Release
  

---

Notes

*1) Use shipped clang

*2) Use qemu-arm to chroot arm distribution

*3) rpi_tools provides arm-linux-gnueabihf-as, this is most important