MB-10701: Fix usage of CMAKE_PREFIX_PATH and other CMake find fixes
Change-Id: Ie55773573ab019ae295a25624bfb15e31c4374c8
Reviewed-on: http://review.couchbase.org/37378
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Chris Hillery <ceej@couchbase.com>