disable kernel build waring

hc

2024-05-10 093a6c67005148ae32a5c9e4553491b9f5c2457b

 kernel/tools/testing/selftests/powerpc/pmu/.gitignore
..
..
@@ -1,3 +1,5 @@
1
+# SPDX-License-Identifier: GPL-2.0-only
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2
 count_instructions
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 l3_bank_test
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 per_event_excludes
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+count_stcx_fail