build: allow BL-specific includes/definitions

This change introduces the `BLx_INCLUDE_DIRS` and `BLx_DEFINES`
Makefile variables, which can be used to append include directories
and preprocessor definitions to specific images created using the
`MAKE_BL` Makefile macro.

Change-Id: I9431f9d1cbde5b0b2624d9ce128a4f043c74c87f
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed