Makefile: Delay expansion of `$(ADAFLAGS)`

This allows users of this library to extend `ADAFLAGS` from within their
Makefile. The added flexibility makes this a very well spent dollar :-)

Change-Id: I873d3eea48549e6945c4229b50c2318a3711bc4d
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/libhwbase/+/43557
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed