message: Fix Linux CI on GitHub
diff: # version of clang we want to use
  CLANG_VERSION=7
  +GITHUB_CLANG_VERSION=8
  # version of libcxx and libcxxabi we want to use
  CXX_VERSION=7.0.0
  # version of CMake to use instead of the default one
  @@ -9,10 +10,17 @@ CMAKE_VERSION=3.13.4
  # version of ninja to use
  NINJA_VERSION=1.8.2
  +# Steps for GitHub Workflows
  +if [[ "$GITHUB_WORKFLOW" ]]]; then
  + sudo wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
  + sudo apt-get install clang-$GITHUB_CLANG_VERSION libc++-$GITHUB_CLANG_VERSION-dev libc++abi-$GITHUB_CLANG_VERSION-dev
  + sudo apt-get install cmake
  +fi
  +
  # Steps specific to our CI environment
  # CI runs on Ubuntu 14.04, we need to install clang-7.0 and the
  # appropriate libc++ ourselves
  -if [[ "$CONTINUOUS_INTEGRATION" ]]; then
  +if [[ "$KOKORO_BUILD_ID" ]]; then
  sudo ln -s /usr/include/x86_64-linux-gnu/asm /usr/include/asm
  if [[ "$FILAMENT_ANDROID_CI_BUILD" ]]; then
  