libperf: Don't remove -g when EXTRA_CFLAGS are used

[ Upstream commit f5b07010c1 ]

When using EXTRA_CFLAGS, for example "EXTRA_CFLAGS=-DREFCNT_CHECKING=1",
this construct stops setting -g which you'd expect would not be affected
by adding extra flags. Additionally, EXTRA_CFLAGS should be the last
thing to be appended so that it can be used to undo any defaults. And no
condition is required, just += appends to any existing CFLAGS and also
appends or doesn't append EXTRA_CFLAGS if they are or aren't set.

It's not clear why DEBUG=1 is required for -g in Perf when in libperf
it's always on, but I don't think we need to change that behavior now
because someone may be depending on it.

Signed-off-by: James Clark <james.clark@linaro.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250319114009.417865-1-james.clark@linaro.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Stable-dep-of: 8c5b40678c ("libperf build: Always place libperf includes first")
Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/lib/perf/Makefile

@@ -54,13 +54,6 @@ endif
 
 TEST_ARGS := $(if $(V),-v)
 
-# Set compile option CFLAGS
-ifdef EXTRA_CFLAGS
-  CFLAGS := $(EXTRA_CFLAGS)
-else
-  CFLAGS := -g -Wall
-endif
-
 INCLUDES = \
 -I$(srctree)/tools/lib/perf/include \
 -I$(srctree)/tools/lib/ \
@@ -70,11 +63,12 @@ INCLUDES = \
 -I$(srctree)/tools/include/uapi
 
 # Append required CFLAGS
-override CFLAGS += $(EXTRA_WARNINGS)
-override CFLAGS += -Werror -Wall
+override CFLAGS += -g -Werror -Wall
 override CFLAGS += -fPIC
 override CFLAGS += $(INCLUDES)
 override CFLAGS += -fvisibility=hidden
+override CFLAGS += $(EXTRA_WARNINGS)
+override CFLAGS += $(EXTRA_CFLAGS)
 
 all: