PHPC-869: Add Mac OS to the operating system matrix

Author: derickr

.evergreen/config.yml

@@ -641,6 +641,9 @@ axes:
       - id: ubuntu1604-arm64
         display_name: "Ubuntu 16.04 ARM64"
         run_on: ubuntu1604-arm64-large
+      - id: osx-1013
+        display_name: "Mac OS 10.13"
+        run_on: osx-1010
 
   - id: storage-engine
     display_name: Storage