Build universal2 macOS binary wheels

Because of the dual build required in macOS it's far easier to embed
yajl into ijson rather than trying to build yajl separately for the two
architectures.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

.github/tools/install_yajl.sh

@@ -10,10 +10,10 @@ install_unix() {
 OS="`uname -s`"
 echo "Building libyajl on $OS"
 case "$OS" in
- MSYS_*|MINGW_*)
- echo "No extra step required in Windows"
+ MSYS_*|MINGW_*|Darwin)
+ echo "No extra step required in Windows or macOS"
  ;;
- Darwin|Linux)
+ Linux)
  install_unix
  ;;
 esac

.travis.yml

@@ -47,6 +47,9 @@ env:
  - CIBW_BEFORE_ALL="bash -c 'cmake --help || yum install -y cmake; cd \"{project}\"; sh .github/tools/install_yajl.sh'"
  - CIBW_TEST_COMMAND="bash -c 'cd \"{project}\"; pytest -vv'"
  - CIBW_ENVIRONMENT_WINDOWS="IJSON_EMBED_YAJL=1"
+ - CIBW_ENVIRONMENT_MACOS="IJSON_EMBED_YAJL=1"
+ - CIBW_ARCHS_MACOS="x86_64 arm64 universal2"
+ - CIBW_TEST_SKIP='*macosx_arm64 *universal2:arm64'
  - TWINE_USERNAME=__token__
 
 _cibuildwheel: &cibuildwheel
@@ -99,7 +102,7 @@ jobs:
  - name: mac wheels build
  <<: *cibuildwheel
  os: osx
- osx_image: xcode10.2
+ osx_image: xcode12.2
  language: shell
  # and a windows build
  - name: windows wheels build