subdir.mk supports absolute path
subdir.mk supports absolute path

Signed-off-by: Pascal Brand <0b55292d2562685bad4ce52d64f802e8f1cd299e@st.com>

chshxi1989/optee_os,matt2048/optee_os,pascal-brand-st-dev/optee_os,chshxi1989/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,cedric-chaumont-st-dev/optee_os,BreezeWu/optee_os,jamescfkung/optee_os,Microsoft/optee_os,matt2048/optee_os,BreezeWu/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os,jamescfkung/optee_os,Microsoft/optee_os,Microsoft/optee_os,cedric-chaumont-st-dev/optee_os,BreezeWu/optee_os,pascal-brand-st-dev/optee_os,cedric-chaumont-st-dev/optee_os,matt2048/optee_os,chshxi1989/optee_os,chshxi1989/optee_os,BreezeWu/optee_os,BreezeWu/optee_os,pascal-brand-st-dev/optee_os,jamescfkung/optee_os,jamescfkung/optee_os,Microsoft/optee_os,cedric-chaumont-st-dev/optee_os,chshxi1989/optee_os,jamescfkung/optee_os