tests: Add 'checkpoint-path' to simpoints stdlib example

The
'configs/example/gem5_library_checkpoints/simpoints-se-checkpoint.py'
example would dump the savepoint in the CWD. This is fine when running
as an example, but we also run this script as a test. In this case the
checkpoint litters the repository.

To fix this, an optional 'checkpoint-path' argument is added to this
example which specifies where the checkpoint is to be saved. In the
tests, the checkpoint is saved to 'tests/gem5/resources'. This is our
default location for resources needed/produced by tests and is ignored
by git.

Change-Id: I3dccc574b9e64d32386fd822ed7248ee365a0a08
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/64092
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/example/gem5_library/checkpoints/simpoints-se-checkpoint.py

@@ -52,6 +52,7 @@ scons build/X86/gem5.opt
 ```
 """
 
+import argparse
 from gem5.simulate.exit_event import ExitEvent
 from gem5.simulate.simulator import Simulator
 from gem5.utils.requires import requires
@@ -68,6 +69,18 @@ from gem5.simulate.exit_event_generators import (
     save_checkpoint_generator,
 )
 
+parser = argparse.ArgumentParser()
+
+parser.add_argument(
+    "--checkpoint-path",
+    type=str,
+    required=False,
+    default="se_checkpoint_folder/",
+    help="The directory to store the checkpoint.",
+)
+
+args = parser.parse_args()
+
 requires(isa_required=ISA.X86)
 
 # When taking a checkpoint, the cache state is not saved, so the cache
@@ -109,7 +122,7 @@ board.set_se_binary_workload(
     simpoint=simpoint,
 )
 
-dir = Path("se_checkpoint_folder/")
+dir = Path(args.checkpoint_path)
 dir.mkdir(exist_ok=True)
 
 simulator = Simulator(