perf build: Pretend scandirat is missing with msan

Memory sanitizer lacks an interceptor for scandirat, reporting all
memory it allocates as uninitialized. Memory sanitizer has a scandir
interceptor so use the fallback function in this case. This allows
'perf test' to run under memory sanitizer.

Additional notes from Ian on running in this mode:

Note, as msan needs to instrument memory allocations libraries need to
be compiled with it. I lacked the msan built libraries and so built
with:
```
$ make -C tools/perf O=/tmp/perf DEBUG=1 EXTRA_CFLAGS="-O0 -g
-fno-omit-frame-pointer -fsanitize=memory
-fsanitize-memory-track-origins" CC=clang CXX=clang++ HOSTCC=clang
NO_LIBTRACEEVENT=1 NO_LIBELF=1 BUILD_BPF_SKEL=0 NO_LIBPFM=1
```
oh, I disabled libbpf here as the bpf system call also lacks msan interceptors.

Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

0 files changed, 0 insertions, 0 deletions