Unlike <PKG>_DEPENDENCIES, <PKG>_PATCH_DEPENDENCIES only guarantees
extract and patch of listed dependencies, not build. Make this subtlety
more explicit in the documentation.
Cc: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
[yann.morin.1998@free.fr: slight fix]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>