src: silence compiler warning node_process_methods

Currently, the following compiler warning is generated by clang:
../src/node_process_methods.cc:71:3:
warning: indirection of non-volatile null pointer will be deleted,
not trap [-Wnull-dereference]
  *static_cast<volatile void**>(nullptr) = nullptr;
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/node_process_methods.cc:71:3: note:
consider using __builtin_trap() or qualifying pointer with 'volatile'
1 warning generated.

This commit adds the volatile qualifier to avoid this warning.

PR-URL: nodejs#28261
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/node_process_methods.cc

@@ -66,7 +66,8 @@ static void Abort(const FunctionCallbackInfo<Value>& args) {
 // For internal testing only, not exposed to userland.
 static void CauseSegfault(const FunctionCallbackInfo<Value>& args) {
   // This should crash hard all platforms.
-  *static_cast<void**>(nullptr) = nullptr;
+  volatile void** d = static_cast<volatile void**>(nullptr);
+  *d = nullptr;
 }
 
 static void Chdir(const FunctionCallbackInfo<Value>& args) {