libcxx on osx

Author: hobu

.github/workflows/build.yml

@@ -39,13 +39,21 @@ jobs:
     - name: Setup micromamba
       uses: mamba-org/provision-with-micromamba@main
       with:
+        miniforge-variant: Mambaforge
+        miniforge-version: latest
+        use-mamba: true
+        auto-update-conda: true
         environment-file: .github/environment.yml
         extra-specs: |
           python=${{ matrix.python-version }}
 
     - name: Install python-pdal
       run: pip install .
 
+    - name: libcxx=14 for OSX
+      if: matrix.os == 'macos-latest'
+      run: mamba install -c conda-forge libcxx=14 -y
+
     - name: Install python-pdal-plugins
       working-directory: ./plugins
       run: pip install .