shared/exec-util: add macro to autoinsert sentinel for fork_agent()

src/shared/exec-util.c

@@ -531,7 +531,7 @@ int fexecve_or_execve(int executable_fd, const char *executable, char *const arg
         return -errno;
 }
 
-int fork_agent(const char *name, const int except[], size_t n_except, pid_t *ret_pid, const char *path, ...) {
+int _fork_agent(const char *name, const int except[], size_t n_except, pid_t *ret_pid, const char *path, ...) {
         bool stdout_is_tty, stderr_is_tty;
         size_t n, i;
         va_list ap;