Fix breakage: bad path join using '/' literal am: 2a5c090c am: cf96d25b...

Fix breakage: bad path join using '/' literal am: 2a5c090c am: cf96d25b am: ec84245e am: c64d309c am: e39804e3

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2052015



Change-Id: Ifeeac49ba35bf142d9c1f540a37c64e6a895a986
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>