[infra] Cleanup better after BuildStats
[infra] Cleanup better after BuildStats

Followup to https://skia-review.googlesource.com/c/skia/+/436816

Change-Id: I564c5a160588e5d9f843e297bf04baea50024dc5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436896
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia