S390:Update inline asm constraint in test-platform

test/cctest/test-platform.cc

Index: test/cctest/test-platform.cc
diff --git a/test/cctest/test-platform.cc b/test/cctest/test-platform.cc
index 9e0016caccb3f515d7687d7f26d29146c3352515..a0fbc21f46220a55d9b6c24e365cebd5feaa41d2 100644
--- a/test/cctest/test-platform.cc
+++ b/test/cctest/test-platform.cc
@@ -25,9 +25,9 @@ void GetStackPointer(const v8::FunctionCallbackInfo<v8::Value>& args) {
 #elif V8_HOST_ARCH_MIPS64
   __asm__ __volatile__("sd $sp, %0" : "=g"(sp_addr));
 #elif defined(__s390x__) || defined(_ARCH_S390X)
-  __asm__ __volatile__("stg 15, %0" : "=g"(sp_addr));
+  __asm__ __volatile__("stg 15, %0" : "=m"(sp_addr));
 #elif defined(__s390__) || defined(_ARCH_S390)
-  __asm__ __volatile__("st 15, %0" : "=g"(sp_addr));
+  __asm__ __volatile__("st 15, %0" : "=m"(sp_addr));
 #elif defined(__PPC64__) || defined(_ARCH_PPC64)
   __asm__ __volatile__("std 1, %0" : "=g"(sp_addr));
 #elif defined(__PPC__) || defined(_ARCH_PPC)