perf test shell vfs_getname: Skip for tools built with NO_LIBDWARF=1

perf test shell vfs_getname: Skip for tools built with NO_LIBDWARF=1

If that is the case, or if the required lib is not present, e.g.
elfutils-devel in Fedora systems, then just skip the tests requiring
DWARF analysis.

Before:

  # rpm -e elfutils-devel
  # perf test ping vfs_getname
  60: Use vfs_getname probe to get syscall args filenames   : FAILED!
  61: probe libc's inet_pton & backtrace it with ping       : Ok
  62: Check open filename arg using perf trace + vfs_getname: FAILED!
  63: Add vfs_getname probe to get syscall args filenames   : FAILED!
  #

After:

  # perf test vfs_getname
  60: Use vfs_getname probe to get syscall args filenames   : Skip
  62: Check open filename arg using perf trace + vfs_getname: Skip
  63: Add vfs_getname probe to get syscall args filenames   : Skip
  #

Then, reinstalling elfutils-devel, rebuilding the tool and running
again:

  # perf test vfs_getname
  60: Use vfs_getname probe to get syscall args filenames   : Ok
  62: Check open filename arg using perf trace + vfs_getname: Ok
  63: Add vfs_getname probe to get syscall args filenames   : Ok
  #

Reported-by: Kim Phillips <kim.phillips@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-d67tvn401fxrwr97pu5ihfb1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>