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