build: try using newer version of xcode/macOS sdk (#22104)

.circleci/config.yml

@@ -65,12 +65,12 @@ machine-linux-2xlarge: &machine-linux-2xlarge
 
 machine-mac: &machine-mac
   macos:
-    xcode: "10.3.0"
+    xcode: "11.1.0"
 
 machine-mac-large: &machine-mac-large
   resource_class: large
   macos:
-    xcode: "10.3.0"
+    xcode: "11.1.0"
 
 # Build configurations options.
 env-debug-build: &env-debug-build