If requirements is not part of BUILD_PROJECTS, assume it was built already
before and set the REQUIREMENTS_TAGGED_PROJECT_REF according to current project.
Otherwise there'd be WHEELS set to something like "requirements:version--distro"
Change-Id: Ifedd3b41a52b4e9628c1b4ec07176b5e3416dbb7
In local dev environment, there can be actions from previous build.
As we are appending actions for per-project build, clear the content
first from last image build execution.
Change-Id: I5c15b5a474a16da5680f3c382154d8bfb9d4731c
