Personal Submodule Forks and Docker Build

- Modify ec, coreboot, and edk submodules to point to personal
  forks using relative URL path
- Add image and script to build firmware in docker container
- Move firmware update build steps from flash.sh to build.sh
  so it can be built inside docker container

docker/Dockerfile

@@ -0,0 +1,67 @@
+FROM ubuntu:20.04
+
+# Install most dependencies
+USER root
+ARG TZ="America/New_York"
+ARG DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && \
+    apt-get upgrade -y && \
+    apt-get install -y --no-install-recommends \
+    adduser \
+    sudo \
+    tzdata \
+    build-essential \
+    ccache \
+    cmake \
+    curl \
+    dosfstools \
+    flashrom \
+    git-lfs \
+    libncurses-dev \
+    libssl-dev \
+    libudev-dev \
+    mtools \
+    parted \
+    pkgconf \
+    python-is-python3 \
+    python3-distutils \
+    uuid-dev \
+    zlib1g-dev \
+    bison \
+    bzip2 \
+    ca-certificates \
+    flex \
+    g++ \
+    gcc \
+    gnat \
+    libnss3-dev \
+    patch \
+    tar \
+    xz-utils \
+    avr-libc \
+    avrdude \
+    clang-format \
+    gcc-avr \
+    libc-dev \
+    libhidapi-dev \
+    libudev-dev \
+    sdcc \
+    shellcheck \
+    xxd
+
+# Create non-root user with disabled password and sudo privileges
+ARG USER=docker
+RUN adduser --disabled-password --gecos '' ${USER}
+RUN adduser ${USER} sudo
+RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
+
+# Enter build directory in user's home
+USER ${USER}
+ARG BUILD_DIR=/home/${USER}/firmware-open
+WORKDIR ${BUILD_DIR}
+
+# Set git configuration (required by some scripts)
+ARG GIT_NAME="Docker User"
+ARG GIT_EMAIL="docker@gmail.com"
+RUN git config --global user.name "${GIT_NAME}"
+RUN git config --global user.email "${GIT_EMAIL}"