[LSC] Add LOCAL_LICENSE_KINDS to external/libbackup

Added SPDX-license-identifier-Apache-2.0 to:
  Android.bp

Bug: 68860345
Bug: 151177513
Bug: 151953481

Test: m all

Exempt-From-Owner-Approval: janitorial work
Change-Id: I0cd18951df69e39be03af00979acad5642d19e54
1 file changed