README: Specify Xcode version.

Fix #21792
servo · Apr 1, 2019 · 6a0c925 · 6a0c925
1 parent 31c0261
commit 6a0c925
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/README.md b/README.md
@@ -51,6 +51,9 @@ Please select your operating system:
 * [Android](#cross-compilation-for-android)
 
 #### macOS
+
+Xcode version 10.2 or above is recommended.
+
 ##### On macOS (homebrew)
 
 ``` sh