windows: revert change to ldebug
ea90ca86664c73fb8d415f3cc7baacdf8a6dd685 ("Move some infra bits of
lib/krb5/ to lib/base/ (2)") inappropriately altered the declaration
of the "ldebug" macro which stores the switches passed to "link.exe".
There is no "/RELEASE" switch and the "/DEBUG" switch instructs the
linker to produce files containing debug symbols (.pdb) which are
required for generating the Windows assemblies.
This change restores the prior behavior.
Change-Id: I61b8fd4759ba84671858f7c8275dbd25af1638e6