sandbox arm64: align stack 16 bytes

sandbox/linux/services/credentials.cc

Index: sandbox/linux/services/credentials.cc
diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index fb6b6b4acab163b33054c8fd63eb004e3a73a268..3052ab7905a9c79d99d9f85988e432f9afb3e663 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -94,7 +94,7 @@ bool ChrootToSafeEmptyDir() {
   // /proc/tid directory for the thread (since /proc may not be aware of the
   // PID namespace). With a process, we can just use /proc/self.
   pid_t pid = -1;
-  char stack_buf[PTHREAD_STACK_MIN];
+  char stack_buf[PTHREAD_STACK_MIN] __attribute__((aligned(16)));
 #if defined(ARCH_CPU_X86_FAMILY) || defined(ARCH_CPU_ARM_FAMILY) || \
     defined(ARCH_CPU_MIPS64_FAMILY) || defined(ARCH_CPU_MIPS_FAMILY)
   // The stack grows downward.