Added -fobjc-arc to support automatic reference counting on macOS

configure

@@ -20385,6 +20385,40 @@ $as_echo "#define SDL_ARM_NEON_BLITTERS 1" >>confdefs.h
     fi
 }
 
+CheckObjectiveCARC()
+{
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for clang -fobjc-arc option" >&5
+$as_echo_n "checking for clang -fobjc-arc option... " >&6; }
+    have_clang_objc_arc=no
+
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$save_CFLAGS -fobjc-arc"
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+    int x = 0;
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  have_clang_objc_arc=yes
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_clang_objc_arc" >&5
+$as_echo "$have_clang_objc_arc" >&6; }
+    CFLAGS="$save_CFLAGS"
+
+    if test x$have_clang_objc_arc = xyes; then
+        EXTRA_CFLAGS="$EXTRA_CFLAGS -fobjc-arc"
+    fi
+}
+
 CheckVisibilityHidden()
 {
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for GCC -fvisibility=hidden option" >&5
@@ -26454,6 +26488,7 @@ $as_echo "#define SDL_VIDEO_RENDER_OGL_ES2 1" >>confdefs.h
         EXTRA_CFLAGS="$EXTRA_CFLAGS -DTARGET_API_MAC_CARBON"
         EXTRA_CFLAGS="$EXTRA_CFLAGS -DTARGET_API_MAC_OSX"
 
+        CheckObjectiveCARC
         CheckVisibilityHidden
         CheckDeclarationAfterStatement
         CheckDummyVideo