linux-user: implement pgid field of /proc/self/stat

Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <mvmfrgzcr4m.fsf@suse.de>

linux-user/syscall.c

@@ -8235,6 +8235,9 @@ static int open_self_stat(CPUArchState *cpu_env, int fd)
         } else if (i == 3) {
             /* ppid */
             g_string_printf(buf, FMT_pid " ", getppid());
+        } else if (i == 4) {
+            /* pgid */
+            g_string_printf(buf, FMT_pid " ", getpgrp());
         } else if (i == 19) {
             /* num_threads */
             int cpus = 0;