Make:Improve directory generation portability.

Make:Improve directory generation portability.

Because of command differences in some build environments the "inline"
method of generating the build directory structure is not portable.
(e.g. in DOS environments the mkdir shell command fails if a directory
already exists, whereas in UNIX environments it succeeds.)

To improve portability we generate the directories needed using make,
but use the "order-only prerequisites" feature of make to prevent writes
of files into the directories generating re-builds, as suggested in the
GNU make Manual (Version 4.1 September 2014).

Change-Id: Ic9af475831063c7fe6f8bccffef184d79e799419