perf build: Disable fewer flex warnings

If flex is version 2.6.4, reduce the number of flex C warnings
disabled. Earlier flex versions have all C warnings disabled.

Committer notes:

Added this to the list of ignored warnings to get it building on
a Fedora 36 machine with flex 2.6.4:

  -Wno-misleading-indentation

Noticed when building with:

  $ make LLVM=1 -C tools/perf NO_BPF_SKEL=1 DEBUG=1

Take two:

We can't just try to canonicalize flex versions by just removing the
dots, as we end up with:

	2.6.4 >= 2.5.37

becoming:

	264 >= 2537

Failing the build on flex 2.5.37, so instead use the back to the past
added $(call version_ge3,$(FLEX_VERSION),2.6.4) variant to check for
that.

Making sure $(FLEX_VERSION) keeps the dots as we may want to use 'sort
-V' or something nicer when available everywhere.

Some other tweaks for other flex versions and combinations with gcc and
clang versions were added, notes on the patch.

Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Gaosheng Cui <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Tom Rix <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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