[PATCH 2/3] selftest/powerpc: Add flags.mk to support pmu buildable

[Madhavan Srinivasan <maddy@linux.ibm.com>]

When running `make -C powerpc/pmu run_tests` from top level selftests
directory, currently this error is being reported

make: Entering directory '/home/maddy/linux/tools/testing/selftests/powerpc/pmu'
Makefile:40: warning: overriding recipe for target 'emit_tests'
../../lib.mk:111: warning: ignoring old recipe for target 'emit_tests'
gcc -m64    count_instructions.c ../harness.c event.c lib.c ../utils.c loop.S  -o /home/maddy/selftest_output//count_instructions
In file included from count_instructions.c:13:
event.h:12:10: fatal error: utils.h: No such file or directory
12 | #include "utils.h"
  |          ^~~~~~~~~
compilation terminated.

This is due to missing of include path in CFLAGS. That is, CFLAGS and
GIT_VERSION macros are defined in the powerpc/ folder Makefile which
in this case not involved.

To address the failure incase of executing specific sub-folder test directly,
a new rule file has been addded by the patch called "flags.mk" under
selftest/powerpc/ folder and is linked to all the Makefile of powerpc/pmu
sub-folders.

Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
---
Changelog RFC:
- Rename the rule file as flags.mk
- Added additional patches to support other sub-folders
  under powerpc/ to be buildable on it own.
link to RFC:
  https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20240225163926.264286-1-maddy@linux.ibm.com/
  
 tools/testing/selftests/powerpc/flags.mk             | 12 ++++++++++++
 tools/testing/selftests/powerpc/pmu/Makefile         |  1 +
 tools/testing/selftests/powerpc/pmu/ebb/Makefile     |  1 +
 .../selftests/powerpc/pmu/event_code_tests/Makefile  |  1 +
 .../selftests/powerpc/pmu/sampling_tests/Makefile    |  1 +
 5 files changed, 16 insertions(+)
 create mode 100644 tools/testing/selftests/powerpc/flags.mk

diff --git a/tools/testing/selftests/powerpc/flags.mk b/tools/testing/selftests/powerpc/flags.mk
new file mode 100644
index 000000000000..28374f470126
--- /dev/null
+++ b/tools/testing/selftests/powerpc/flags.mk
@@ -0,0 +1,12 @@
+#This checks for any ENV variables and add those.
+
+#ifeq ($(GIT_VERSION),)
+GIT_VERSION = $(shell git describe --always --long --dirty || echo "unknown")
+export GIT_VERSION
+#endif
+
+#ifeq ($(CFLAGS),)
+CFLAGS := -std=gnu99 -O2 -Wall -Werror -DGIT_VERSION='"$(GIT_VERSION)"' -I$(selfdir)/powerpc/include $(CFLAGS)
+export CFLAGS
+#endif
+
diff --git a/tools/testing/selftests/powerpc/pmu/Makefile b/tools/testing/selftests/powerpc/pmu/Makefile
index a284fa874a9f..1fcacae1b188 100644
--- a/tools/testing/selftests/powerpc/pmu/Makefile
+++ b/tools/testing/selftests/powerpc/pmu/Makefile
@@ -7,6 +7,7 @@ EXTRA_SOURCES := ../harness.c event.c lib.c ../utils.c
 
 top_srcdir = ../../../../..
 include ../../lib.mk
+include ../flags.mk
 
 all: $(TEST_GEN_PROGS) ebb sampling_tests event_code_tests
 
diff --git a/tools/testing/selftests/powerpc/pmu/ebb/Makefile b/tools/testing/selftests/powerpc/pmu/ebb/Makefile
index b3946ce17e0c..1b39af7c10db 100644
--- a/tools/testing/selftests/powerpc/pmu/ebb/Makefile
+++ b/tools/testing/selftests/powerpc/pmu/ebb/Makefile
@@ -18,6 +18,7 @@ TEST_GEN_PROGS := reg_access_test event_attributes_test cycles_test	\
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk
+include ../../flags.mk
 
 # The EBB handler is 64-bit code and everything links against it
 CFLAGS += -m64
diff --git a/tools/testing/selftests/powerpc/pmu/event_code_tests/Makefile b/tools/testing/selftests/powerpc/pmu/event_code_tests/Makefile
index 509d4b235b9e..fdb080b3fa65 100644
--- a/tools/testing/selftests/powerpc/pmu/event_code_tests/Makefile
+++ b/tools/testing/selftests/powerpc/pmu/event_code_tests/Makefile
@@ -9,6 +9,7 @@ TEST_GEN_PROGS := group_constraint_pmc56_test group_pmc56_exclude_constraints_te
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk
+include ../../flags.mk
 
 CFLAGS += -m64
 
diff --git a/tools/testing/selftests/powerpc/pmu/sampling_tests/Makefile b/tools/testing/selftests/powerpc/pmu/sampling_tests/Makefile
index d45892151e05..9f79bec5fce7 100644
--- a/tools/testing/selftests/powerpc/pmu/sampling_tests/Makefile
+++ b/tools/testing/selftests/powerpc/pmu/sampling_tests/Makefile
@@ -9,6 +9,7 @@ TEST_GEN_PROGS := mmcr0_exceptionbits_test mmcr0_cc56run_test mmcr0_pmccext_test
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk
+include ../../flags.mk
 
 CFLAGS += -m64
 
-- 
2.43.2