libqmi: musl compat canonicalize_file_name

libqmi: musl compat canonicalize_file_name

Adds an inline equivalent of canonicalize_file_name
using realpath().

Bug report (origin of this patch):
https://bugs.freedesktop.org/show_bug.cgi?id=99944

Resolves:
http://autobuild.buildroot.net/results/afa/afa4b97e012586585b11be1e70ed3c63a7c48a4d/

  CCLD     test-generated
  CCLD     test-utils
  CCLD     test-message
../../../src/libqmi-glib/.libs/libqmi-glib.so: undefined reference to `canonicalize_file_name'
collect2: error: ld returned 1 exit status
Makefile:440: recipe for target 'test-generated' failed

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>