Migrate from CircleCI 1.0 to 2.0

Update circle.yml to the new format .circleci/config.yml
Update install-toolchain.sh to the more robust version from dap42

.circleci/config.yml

@@ -0,0 +1,25 @@
+version: 2
+jobs:
+  build:
+    machine: true
+    steps:
+      - checkout
+      - run:
+          name: Checkout submodules
+          command: git submodule sync && git submodule update --init
+      - restore_cache:
+          key: v1-toolchain-checksum-{{ checksum "util/install-toolchain.sh" }}
+      - run:
+          name: Install toolchain
+          command: ./util/install-toolchain.sh
+      - save_cache:
+          key: v1-toolchain-checksum-{{ checksum "util/install-toolchain.sh" }}
+          paths:
+            - "~/toolchains/"
+      - run:
+          name: Compile firmware
+          command: make -f release.Makefile -k all
+          environment:
+            PREFIX: "~/toolchains/gcc-arm-embedded/bin/arm-none-eabi"
+      - store_artifacts:
+          path: build/

util/install-toolchain.sh

@@ -1,8 +1,32 @@
 #!/bin/bash
+set -eo pipefail
 URL=https://developer.arm.com/-/media/Files/downloads/gnu-rm/6-2017q2/gcc-arm-none-eabi-6-2017-q2-update-linux.tar.bz2
 TOOLCHAIN=gcc-arm-none-eabi-6-2017-q2-update
-if [[ ! -d "$HOME/toolchains/gcc-arm-embedded" ]]; then
-    mkdir -p ~/toolchains
-    wget -qO- $URL | tar xj -C ~/toolchains/
-    ln -s $TOOLCHAIN ~/toolchains/gcc-arm-embedded
+TOOLCHAINS=$HOME/toolchains
+TOOLCHAIN_MISSING=0
+GCC=${TOOLCHAINS}/gcc-arm-embedded/bin/arm-none-eabi-gcc
+if [[ ! -d "${TOOLCHAINS}/gcc-arm-embedded" ]]; then
+    TOOLCHAIN_MISSING=1
 fi;
+if [[ ! -f ${GCC} ]]; then
+    TOOLCHAIN_MISSING=1
+fi;
+
+if [ $TOOLCHAIN_MISSING -eq 1 ]; then
+    echo "Installing $TOOLCHAIN from $URL to ${TOOLCHAINS}"
+    mkdir -p ${TOOLCHAINS}
+    wget -qO- $URL | tar xj -C ${TOOLCHAINS}
+    rm -rf ${TOOLCHAINS}/gcc-arm-embedded
+    ln -s $TOOLCHAIN ${TOOLCHAINS}/gcc-arm-embedded
+fi;
+
+EXISTING_TOOLCHAIN=`readlink -f "${TOOLCHAINS}/gcc-arm-embedded"`
+echo "Current toolchain is $EXISTING_TOOLCHAIN"
+
+if ! ldd ${GCC} >/dev/null; then
+    echo "${GCC} does not appear to be executable on this machine"
+    exit 1
+fi;
+
+TOOLCHAIN_VER=`${GCC} --version | head -n 1`
+echo "Installed toolchain version is $TOOLCHAIN_VER"