perf build: Fix LIBTRACEEVENT_DYNAMIC

perf build: Fix LIBTRACEEVENT_DYNAMIC

The tools/lib includes fixes break LIBTRACEVENT_DYNAMIC as the makefile
erroneously had dependencies on building libtraceevent even when not
linking with it. This change fixes the issues with LIBTRACEEVENT_DYNAMIC
by making the built files optional.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: bpf@vger.kernel.org
Link: http://lore.kernel.org/lkml/20221116224631.207631-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>