perf tools: Add includes for detected configs in Makefile.perf

perf tools: Add includes for detected configs in Makefile.perf

Makefile.perf uses "CONFIG_*" checks in the code. Example the config for
libtraceevent is used to set PYTHON_EXT_SRCS

	ifeq ($(CONFIG_LIBTRACEEVENT),y)
	  PYTHON_EXT_SRCS := $(shell grep -v ^\# util/python-ext-sources)
	else
	  PYTHON_EXT_SRCS := $(shell grep -v '^\#\|util/trace-event.c' util/python-ext-sources)
	endif

But this is not picking the value for CONFIG_LIBTRACEEVENT that is set
using the settings in Makefile.config. Include the file
".config-detected" so that make will use the system detected
configuration in the CONFIG checks.

This will fix isues that could arise when other "CONFIG_*" checks are
added to Makefile.perf in future as well.

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Disha Goel <disgoel@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20230912063807.74250-1-atrajeev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>