tools build: Add detected config support

tools build: Add detected config support

Adding support to include detected configuration makefile into the build
process. This will allow the Build objects to be configurable based on
the config data, like:

  perf-$(CONFIG_KRAVA) += krava.o

The configuration is stored in '.config-detected' file, which is
generated for each compilation.

Signed-off-by: Jiri Olsa <[email protected]>
Tested-by: Sukadev Bhattiprolu <[email protected]>
Tested-by: Will Deacon <[email protected]>
Cc: Alexis Berlemont <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Corey Ashford <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>