Fix detection of CMake-built glog on Windows.

- glog has a bug in its CMakeLists.txt whereby it uses ‘google-glog’ as
  its project() name in its CMakeLists.txt, but exports itself as ‘glog’
  which results in an install prefix on Windows which contains
  ‘google-glog’ instead of ‘glog’ which breaks find_package(glog).
  This has been raised as a glog issue here:
  https://github.com/google/glog/issues/149.
- We now force find_package(glog) to search glog using both
  ‘google-glog’ (for Windows) & ‘glog’ (for all other OSs).

Change-Id: I6c0edccdec405200eaa0fea1476b574e73bd3f14