perf tools: Don't include signature in version strings

perf tools: Don't include signature in version strings

This explodes the build if HEAD is signed, since the generated version
is gpg: Signature made Mon 26 Dec 2022 20:34:48 CET, then a few more
lines, then the SHA.

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/7c9637711271f50ec2341fb8a7c29585335dab04.1672174189.git.nabijaczleweli@nabijaczleweli.xyz
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>