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

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



Change-Id: Iaf7f77c3f1505845b1436c0fd922b0bb53bd8fe3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>