selftests: introduce gen_tar Makefile target

The gen_kselftest_tar.sh always packages *all* selftests and doesn't
pass along any variables to `make install` to influence what should be
built. This can result in an early error on the command line ("Unknown
tarball format TARGETS=XXX"), or unexpected test failures as the
tarball contains tests people wanted to skip on purpose.

Since the makefile already contains all the logic, we can add a target
for packaging. Keep the default .gz target the script uses, and actually
extend the supported formats by using tar's autodetection.

To not break current workflows, keep the gen_kselftest_tar.sh script as
it is, with an added suggestion to use the makefile target instead.

Signed-off-by: Veronika Kabatova <vkabatov@redhat.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 2ff6870..1195bd8 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -249,10 +249,17 @@
 	$(error Error: set INSTALL_PATH to use install)
 endif
 
+FORMAT ?= .gz
+TAR_PATH = $(abspath ${INSTALL_PATH}/kselftest-packages/kselftest.tar${FORMAT})
+gen_tar: install
+	@mkdir -p ${INSTALL_PATH}/kselftest-packages/
+	@tar caf ${TAR_PATH} --exclude=kselftest-packages -C ${INSTALL_PATH} .
+	@echo "Created ${TAR_PATH}"
+
 clean:
 	@for TARGET in $(TARGETS); do \
 		BUILD_TARGET=$$BUILD/$$TARGET;	\
 		$(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET clean;\
 	done;
 
-.PHONY: khdr all run_tests hotplug run_hotplug clean_hotplug run_pstore_crash install clean
+.PHONY: khdr all run_tests hotplug run_hotplug clean_hotplug run_pstore_crash install clean gen_tar