Generate SBoM Manifest fails in source-only validation due to missing BuildDropPath

[DonnaChen888]

Repro Pipeline:
20260309.11

Repro Branch:
10.0.1xx

Error Message:
BuildDropPath directory not found for '/__w/1/s/src/sdk/artifacts/packages/Release/Shipping'
##[error]Manifest generation failed, please check output file for more info.