package/lttng-tools: backport patch fixing pthread_setname_np failure

This patch, backported from upstream, prevent the build from failing due
to:

  [...]
    CCLD     lttng-consumerd
  ../../../src/common/.libs/libcommon.a(runas.o): In function `run_as_worker':
  /tmp/br/build/lttng-tools-2.7.0/src/common/runas.c:325: undefined reference to `pthread_setname_np'
  collect2: error: ld returned 1 exit status
  Makefile:475: recipe for target 'lttng-consumerd' failed
  [...]

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>