The simpletrace SystemTap tapset outputs simpletrace binary traces for
SystemTap probes.  This is useful because SystemTap has no default way
to format or store traces.  The simpletrace SystemTap tapset provides an
easy way to store traces.

The simpletrace.py tool or custom Python scripts using the
simpletrace.py API can analyze SystemTap these traces:

  $ ./configure --enable-trace-backends=dtrace ...
  $ make && make install
  $ stap -e 'probe qemu.system.x86_64.simpletrace.* {}' \
         -c qemu-system-x86_64 >/tmp/trace.out
  $ scripts/simpletrace.py --no-header trace-events /tmp/trace.out
  g_malloc 4.531 pid=15519 size=0xb ptr=0x7f8639c10470
  g_malloc 3.264 pid=15519 size=0x300 ptr=0x7f8639c10490
  g_free 5.155 pid=15519 ptr=0x7f8639c0f7b0

Note that, unlike qemu-system-x86_64.stp and
qemu-system-x86_64.stp-installed, only one file is needed since the
simpletrace SystemTap tapset does not reference the QEMU binary by path.
Therefore it doesn't matter whether the QEMU binary is installed or not.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>