Enable universal2 wheels

Changes ported from `numpy-wheels`  found at:
- MacPython/numpy-wheels#104
- MacPython/numpy-wheels#115

azure-pipelines.yml

@@ -38,13 +38,21 @@ jobs:
   - template: azure-posix.yml
     parameters:
       name: macOS
-      vmImage: macOS-10.14
+      vmImage: macOS-10.15
       matrix:
         osx-Py37:
           MB_PYTHON_VERSION: "3.7"
         osx-Py38:
           MB_PYTHON_VERSION: "3.8"
           MB_PYTHON_OSX_VER: "10.9"
+        osx-Py38-universal2:
+          MB_PYTHON_VERSION: "3.8"
+          MB_PYTHON_OSX_VER: "10.9"
+          PLAT: universal2
         osx-Py39:
           MB_PYTHON_VERSION: "3.9"
           MB_PYTHON_OSX_VER: "10.9"
+        osx-Py39-universal2:
+          MB_PYTHON_VERSION: "3.9"
+          MB_PYTHON_OSX_VER: "10.9"
+          PLAT: universal2

azure-posix.yml

@@ -56,8 +56,9 @@ jobs:
         displayName: Define build env variables
 
       - bash: |
-          set -e
+          set -ex
           echo building for commit "$BUILD_COMMIT"
+
           pip install --upgrade virtualenv wheel setuptools
           BUILD_DEPENDS="wheel oldest-supported-numpy Cython>=0.29.18 pybind11>=2.4.3 pythran"
 

config.sh

@@ -16,12 +16,29 @@ function build_wheel {
     fi
 }
 
+# TODO: Remove once https://github.com/matthew-brett/multibuild/pull/409 lands
+function pyinst_fname_for_version {
+    # echo filename for OSX installer file given Python and minimum
+    # macOS versions
+    # Parameters
+    #   $py_version (Python version in major.minor.extra format)
+    #   $py_osx_ver: {major.minor | not defined}
+    #       if defined, the minimum macOS SDK version that Python is
+    #       built for, eg: "10.6" or "10.9", if not defined, infers
+    #       this from $py_version using macpython_sdk_for_version
+    local py_version=$1
+    local py_osx_ver=${2:-$(macpython_sdk_for_version $py_version)}
+    local inst_ext=$(pyinst_ext_for_version $py_version)
+    echo "python-${py_version}-macosx${py_osx_ver}.${inst_ext}"
+}
+
 function build_libs {
     PYTHON_EXE=`which python`
     $PYTHON_EXE -c"import platform; print('platform.uname().machine', platform.uname().machine)"
     basedir=$($PYTHON_EXE scipy/tools/openblas_support.py)
-    $use_sudo cp -r $basedir/lib/* /usr/local/lib
-    $use_sudo cp $basedir/include/* /usr/local/include
+    $use_sudo cp -r $basedir/lib/* $BUILD_PREFIX/lib
+    $use_sudo cp $basedir/include/* $BUILD_PREFIX/include
+    export OPENBLAS=$BUILD_PREFIX
 }
 
 function set_arch {