app-shells/bash: fix CVE-2019-9924. BUG=b/269241909 TEST=presubmit RELEASE_NOTE=Fixed CVE-2019-9924. cos-patch: security-high Change-Id: I28fb2bf4f1e742ebddac96b828f6038ef0bb3079 Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/portage-stable/+/43890 Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com> Reviewed-by: Meena Shanmugam <meenashanmugam@google.com> Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>