resources: add packer to gitignore

Change-Id: I0cd035e9e32e7dda38319d49b1a03cbbf8370c2b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-resources/+/32335
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/src/boot-exit/.gitignore b/src/boot-exit/.gitignore
new file mode 100644
index 0000000..541dc15
--- /dev/null
+++ b/src/boot-exit/.gitignore
@@ -0,0 +1,4 @@
+**packer
+**packer_*.zip
+packer_cache/
+disk-image/boot-exit/boot-exit-image/boot-exit