build: Link libglapi with pthreads

NOTE: This is a candidate for the 9.0 branch.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=839060
          https://bugs.gentoo.org/show_bug.cgi?id=435152
Reviewed-by: Adam Jackson <ajax@redhat.com>
diff --git a/configure.ac b/configure.ac
index 49cdb82..896f98a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -524,6 +524,7 @@
     SELINUX_LIBS="-lselinux"
     DEFINES="$DEFINES -DMESA_SELINUX"
 fi
+AC_SUBST([SELINUX_LIBS])
 
 dnl Options for APIs
 AC_ARG_ENABLE([opengl],
@@ -920,10 +921,6 @@
 AC_SUBST([GLESv2_LIB_DEPS])
 AC_SUBST([GLESv2_PC_LIB_PRIV])
 
-GLAPI_LIB_DEPS="-lpthread $SELINUX_LIBS"
-AC_SUBST([GLAPI_LIB_DEPS])
-
-
 DRI_LIB_DEPS="\$(top_builddir)/src/mesa/libdricore/libdricore${VERSION}.la"
 
 AC_SUBST([HAVE_XF86VIDMODE])