experimental/tools/pdf-comparison: delete worktree when it gets into a bad state
experimental/tools/pdf-comparison: delete worktree when it gets into a bad state

No-Try: true
Change-Id: I61f48fd32348d44a2c7e27d56e404f7876bed3ef
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/245161
Reviewed-by: Hal Canary <fd9641b23487c8ee78406c27513624c460600766@google.com>
Commit-Queue: Hal Canary <fd9641b23487c8ee78406c27513624c460600766@google.com>

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