PPC: Use builtin D-Cache/I-Cache sync code.

src/lj_vm.h

@@ -27,6 +27,9 @@ LJ_ASMF void lj_vm_unwind_rethrow(void);
 #if LJ_TARGET_X86ORX64
 LJ_ASMF int lj_vm_cpuid(uint32_t f, uint32_t res[4]);
 #endif
+#if LJ_TARGET_PPC
+void lj_vm_cachesync(void *start, void *end);
+#endif
 LJ_ASMF double lj_vm_foldarith(double x, double y, int op);
 #if LJ_HASJIT
 LJ_ASMF double lj_vm_foldfpm(double x, int op);