Tweak build matrix

Author: lefticus

.github/workflows/ci.yml

@@ -50,8 +50,21 @@ jobs:
           # mingw is determined by this author to be too buggy to support
           - os: windows-2019
             compiler: gcc-8
-          - os: windows-2019
+
+              #          - os: windows-2019
+              #compiler: llvm
+
+          # These have anonalous failures, not sure what is up with no access to a physical Mac.
+          - os: macos-10.15
+            compiler: gcc-8
+            build_type: Debug
+            developer_mode: ON
+          - os: macos-10.15
             compiler: llvm
+            build_type: Release
+            developer_mode: ON
+
+
 
         include:
           # This exists solely to make sure a non-multiconfig build works