oeqa/selftest/sstatetests: Add easier debug option

In order to debug these selftest failures you end up having to comment out
the file cleanup. Make this an option at the top of the file to make it
a bit easier, I've had to do this too many times now.

(From OE-Core rev: ae69d48b0e5b58b18553a6b3cd03ffbd3f369aa3)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/selftest/cases/sstatetests.py

@@ -18,6 +18,9 @@ from oeqa.selftest.case import OESelftestTestCase
 import oe
 import bb.siggen
 
+# Set to True to preserve stamp files after test execution for debugging failures
+keep_temp_files = False
+
 class SStateBase(OESelftestTestCase):
 
     def setUpLocal(self):
@@ -35,6 +38,10 @@ class SStateBase(OESelftestTestCase):
         self.target_os = bb_vars['TARGET_OS']
         self.distro_specific_sstate = os.path.join(self.sstate_path, self.hostdistro)
 
+    def track_for_cleanup(self, path):
+        if not keep_temp_files:
+            super().track_for_cleanup(path)
+
     # Creates a special sstate configuration with the option to add sstate mirrors
     def config_sstate(self, temp_sstate_location=False, add_local_mirrors=[]):
         self.temp_sstate_location = temp_sstate_location