stdlib,configs: Set SPEC examples partition param to optional

The SPEC2006 and SPEC2017 example configs require the passing of SPEC
disk image to function correctly. Prior to this commit a root partition
parameter was required. However, disk images don't necessarily have
partitions. In this case an empty string needed passed.

This patch makes the root partition parameter optional. If a disk image
does not have a root partition, it does not need specified.

Change-Id: Ic0093c70c72ab83ffaca54c8ad24245d84a5e5ba
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/53846
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
diff --git a/configs/example/gem5_library/x86-spec-cpu2006-benchmarks.py b/configs/example/gem5_library/x86-spec-cpu2006-benchmarks.py
index 5624eaf..c1b7a3b 100644
--- a/configs/example/gem5_library/x86-spec-cpu2006-benchmarks.py
+++ b/configs/example/gem5_library/x86-spec-cpu2006-benchmarks.py
@@ -117,7 +117,8 @@
 parser.add_argument(
     "--partition",
     type = str,
-    required = True,
+    required = False,
+    default=None,
     help = "Input the root partition of the SPEC disk-image. If the disk is \
     not partitioned, then pass \"\"."
 )
diff --git a/configs/example/gem5_library/x86-spec-cpu2017-benchmarks.py b/configs/example/gem5_library/x86-spec-cpu2017-benchmarks.py
index 25bbbea..2a03389 100644
--- a/configs/example/gem5_library/x86-spec-cpu2017-benchmarks.py
+++ b/configs/example/gem5_library/x86-spec-cpu2017-benchmarks.py
@@ -123,7 +123,8 @@
 parser.add_argument(
     "--partition",
     type = str,
-    required = True,
+    required = False,
+    default=None,
     help = "Input the root partition of the SPEC disk-image. If the disk is \
     not partitioned, then pass \"\"."
 )