sandbox arm64: align stack 16 bytes

base/process/launch_posix.cc

Index: base/process/launch_posix.cc
diff --git a/base/process/launch_posix.cc b/base/process/launch_posix.cc
index 4bd3da312a6ee54ea0d1eb2ead985322404bd309..4019de586fbcb155ed68d013e431e875411c86ba 100644
--- a/base/process/launch_posix.cc
+++ b/base/process/launch_posix.cc
@@ -736,7 +736,7 @@ NOINLINE pid_t CloneAndLongjmpInChild(unsigned long flags,
   // internal pid cache. The libc interface unfortunately requires
   // specifying a new stack, so we use setjmp/longjmp to emulate
   // fork-like behavior.
-  char stack_buf[PTHREAD_STACK_MIN];
+  char stack_buf[PTHREAD_STACK_MIN] ALIGNAS(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.