Update and fix Mac CI builds

- GitHub discontinued Actions runners for macos-10 and macos-11, so we
  build cboe on macos-12 now
- The path to Xcode.app has changed
- mac scons build wanted a new include statement for vector
- hint scons to look for boost 1.85, not 1.58.

.github/workflows/ci.yml

@@ -12,9 +12,9 @@
 
 	jobs: {
 		macos-xcode: {
-			runs-on: macos-10.15,
+			runs-on: macos-12,
 			env: {
-				DEVELOPER_DIR: /Applications/Xcode_12.4.app/Contents/Developer
+				DEVELOPER_DIR: /Applications/Xcode_13.4.app/Contents/Developer
 			},
 			steps: [
 				{
@@ -45,7 +45,7 @@
 			]
 		},
 		macos-scons: {
-			runs-on: macos-10.15,
+			runs-on: macos-12,
 			steps:  [
 				{
 					name: checkout,