Revert "Force-replace all Zi and ZI with Z7 so that there are no separate pdb."

This commit causes Visual Studio to always compile the objects.
Possibly it notices that the objects were compiled with Z7
instead of Zi or ZI.  Or it may look for the pdb files because they
are listed in cl.write.1.tlog, not find them, and force a build.

This reverts commit f254fa8fd73b39da44a0f2bac7e890a4db8252bf.