Remove obsolete PDK build functionality

This hasn't worked for a couple years, and continues to bitrot. Just
remove it.

Adds a bpfix rule so that we can eventually remove the
product_variables.pdk definition, which is now always a no-op.

Test: treehugger
Change-Id: I830b54d419b59f6db1d4617b45e61a78234f57a7
Merged-In: I830b54d419b59f6db1d4617b45e61a78234f57a7