tracing: install trace events file only if necessary

It is not useful when configuring with --enable-trace-backends=nop.

Signed-off-by: Carlos Santos <casantos@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230408010410.281263-1-casantos@redhat.com>

trace/meson.build

@@ -64,7 +64,7 @@ trace_events_all = custom_target('trace-events-all',
                                  input: trace_events_files,
                                  command: [ 'cat', '@INPUT@' ],
                                  capture: true,
-                                 install: true,
+                                 install: get_option('trace_backends') != [ 'nop' ],
                                  install_dir: qemu_datadir)
 
 if 'ust' in get_option('trace_backends')