configs: Assign the host gid to the Process.gid in SE configs

Some syscalls (like chown) can make use of the current process group id
(gid) to setup file ownership. If we just provide the default fake gid
([1]) we will encounter some problems when executing the syscall on the
host.

Example (guest) program:

gid_t prc_gid = getgid();
int res = chown(..., prc_gid);

By assigning the host gid to the guest we are sure we can successfully
execute syscalls from the gem5 process

[1]: https://github.com/gem5/gem5/blob/v21.1.0.2/src/sim/Process.py#L52

Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Change-Id: Ia09f44916def03f68f7605d72f323f03ec71bbe1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/51767
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/example/arm/starter_se.py

@@ -140,6 +140,7 @@ def get_processes(cmd):
         argv = shlex.split(c)
 
         process = Process(pid=100 + idx, cwd=cwd, cmd=argv, executable=argv[0])
+        process.gid = os.getgid()
 
         print("info: %d. command and arguments: %s" % (idx + 1, process.cmd))
         multiprocesses.append(process)

configs/example/se.py

@@ -88,6 +88,7 @@ def get_processes(args):
         process = Process(pid = 100 + idx)
         process.executable = wrkld
         process.cwd = os.getcwd()
+        process.gid = os.getgid()
 
         if args.env:
             with open(args.env, 'r') as f: