Merges build file structure so that both libteec and optee_supplicant
are under the same nuttx-app directory. This better reflects external
source repo structrure (optee_client containing both libteec and
tee-supplicant) and avoids a case where build of supplicant
was attempted before libteec, leading to a missing .zip file
(zip file was only downloaded by libteec, but order of builds was
not enforced).
Signed-off-by: George Poulios <gpoulios@census-labs.com>
