Win32: fix cppunit test strangeness.

Appending items to our search path for libraries leaves us vulnerable
to similarly named libraries in the system. In my case some
$HOME/AMD APP SDK/2.9/bin/x86/glew32.dll presumably incompatible
with our internal version. Hence prepend important path elements to
better match our program/ setup at run-time.

Change-Id: Iecf266a9d14d71de6c2e402793339e579ec0b987