When pkg-config-0.28 is configured with "--with-internal-glib" the following error occurs on systems running older Kernels that don't have PR_SET_NAME defined for prctl(2):

[...]
  CC       gthread-posix.lo
gthread-posix.c: In function `g_system_thread_set_name':
gthread-posix.c:1175: error: `PR_SET_NAME' undeclared (first use in this function)
gthread-posix.c:1175: error: (Each undeclared identifier is reported only once
gthread-posix.c:1175: error: for each function it appears in.)

I believe that the following patch can fix it (at least it worked for me here on a RHEL4 system running kernel 2.6.9-100.ELsmp):

*** glib/glib/gthread-posix.c.orig      2015-09-14 12:18:16.000000000 -0400
--- glib/glib/gthread-posix.c   2015-09-14 12:18:35.000000000 -0400
***************
*** 1171,1177 ****
  void
  g_system_thread_set_name (const gchar *name)
  {
! #ifdef HAVE_SYS_PRCTL_H
    prctl (PR_SET_NAME, name, 0, 0, 0, 0);
  #endif
  }
--- 1171,1177 ----
  void
  g_system_thread_set_name (const gchar *name)
  {
! #if HAVE_SYS_PRCTL_H && defined PR_SET_NAME
    prctl (PR_SET_NAME, name, 0, 0, 0, 0);
  #endif
  }