selftests/bpf: add pyperf scale test

Add a snippet of pyperf bpf program used to collect python stack traces
as a scale test for the verifier.

At 189 loop iterations llvm 9.0 starts ignoring '#pragma unroll'
and generates partially unrolled loop instead.
Hence use 50, 100, and 180 loop iterations to stress test.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/progs/pyperf50.c

@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#define STACK_MAX_LEN 50
+#include "pyperf.h"