config: fix building for iOS

otherwise failing to link because the builtin is not provided as shown
by :

  $ CC='xcrun -sdk iphoneos clang -arch arm64' make
  Undefined symbols for architecture arm64:
    "___clear_cache", referenced from:
        _sljit_generate_code in sljitLir-c23a56.o
        _sljit_set_jump_addr in sljitLir-c23a56.o
        _sljit_set_const in sljitLir-c23a56.o
  ld: symbol(s) not found for architecture arm64

sljit_src/sljitConfigInternal.h

@@ -322,8 +322,10 @@ extern "C" {
 #if (!defined SLJIT_CACHE_FLUSH && defined __has_builtin)
 #if __has_builtin(__builtin___clear_cache)
 
+#ifndef __APPLE__
 #define SLJIT_CACHE_FLUSH(from, to) \
 	__builtin___clear_cache((char*)(from), (char*)(to))
+#endif
 
 #endif /* __has_builtin(__builtin___clear_cache) */
 #endif /* (!defined SLJIT_CACHE_FLUSH && defined __has_builtin) */
@@ -336,7 +338,7 @@ extern "C" {
 #define SLJIT_CACHE_FLUSH(from, to)
 
 #elif defined __APPLE__
-
+#include <libkern/OSCacheControl.h>
 /* Supported by all macs since Mac OS 10.5.
    However, it does not work on non-jailbroken iOS devices,
    although the compilation is successful. */