For regular modules, adding files to BLOBS is sufficient to create the
corresponding headers.
Application modules are different, as they use a minimal makefile
(makefiles.application.inc.mk) to build, thus application level
variables are not available.
This commit makes Makefile.include pass BLOBS to the application
Makefile as APPLICATION_BLOBS, and application.inc.mk use that variable
as value for BLOBS.
The indirection is necessary so submakefiles (e.g., those visited by
DIRS) do not hard override BLOBS.
Kaspar Schleiser
b4da3b464f