text: Title: Makefile: add a DBG variable
  Body: Now `make DBG=1` will produce binaries with no optimizaions and no inlining, but with symbols and DWARF information.
  
  This also sets the various compile flags to use "all=" syntax.  Otherwise things like trimpath only apply to the CLI-listed packages and nothing else (which seems egregiously wrong).
  
  Worth noting: this builds tools (like codegens) with debugging too.  We could make it more sophisticated if that seems a problem (e.g.  a different flag or value)
  
  To discuss: "DBG" vs "KUBE_DBG" vs `make debug` vs ...
  
  /kind cleanup
  
  ```release-note
  NONE
  ```
  