SDL: cmake: Correctly set IOS variable.

SDL Commits
1 
From f306662544d20b435c24265598e276239b23c0e1 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 5 Oct 2021 11:13:41 -0400
Subject: [PATCH] cmake: Correctly set IOS variable.

Fixes #4635.
---
 CMakeLists.txt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d4a041b579..a6548095f9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -128,8 +128,12 @@ elseif(APPLE)
     set(MACOSX TRUE)
   elseif(CMAKE_SYSTEM_NAME MATCHES ".*tvOS.*")
     set(TVOS TRUE)
+  elseif(CMAKE_SYSTEM_NAME MATCHES ".*iOS.*")
+    # !!! FIXME: remove the version check when we start requiring >= 3.14.0
+    if(CMAKE_VERSION VERSION_LESS 3.14)
+      set(IOS TRUE)
+    endif()
   endif()
-  # TODO: iOS?
 elseif(CMAKE_SYSTEM_NAME MATCHES "BeOS.*")
   message_error("BeOS support has been removed as of SDL 2.0.2.")
 elseif(CMAKE_SYSTEM_NAME MATCHES "Haiku.*")