Fix breakage: bad path join using '/' literal am: 2a5c090c am: cf96d25b am: ec84245e am: c64d309c am: e39804e3 am: 5a0dbab4

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



Change-Id: I478620391ad7dd523cdb1f05d19cd5f7cd3114f6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>