linux: Fix stack-related sub-process shutdown crashes (fixes #3912)

On Linux systems the stack frame reference canary will be purposely
changed when forking sub-processes (see https://crbug.com/40181003).
To avoid sub-process shutdown crashes the NO_STACK_PROTECTOR
annotation must be added to all functions in the call stack leading to
CefExecuteProcess(). Applications that cannot add this annotation must
instead pass the `--change-stack-guard-on-fork=disable` command-line
flag.

libcef/browser/main_runner.cc

@@ -206,6 +206,7 @@ void CefMainRunner::QuitMessageLoop() {
 }
 
 // static
+NO_STACK_PROTECTOR
 int CefMainRunner::RunAsHelperProcess(const CefMainArgs& args,
                                       CefRefPtr<CefApp> application,
                                       void* windows_sandbox_info) {