fontconfig: Adjust buildlink3.mk to possibly use builtin one in NetBSD

In NetBSD, builtin fontconfig has an internal and with symbols
renamed libuuid (libuuid_ul). Avoid including it in that case.

Problem originally analyzed by <wiz> in:

 <https://mail-index.NetBSD.org/tech-pkg/2019/06/19/msg021438.html>

XXX: As <mrg> pointed out in that thread probably uuid bl3 should not
XXX: be included there at all. `cvs annotate' and `cvs log' does not
XXX: contain any rationale in adding it.

Index: buildlink3.mk
===================================================================
RCS file: /cvsroot/pkgsrc/fonts/fontconfig/buildlink3.mk,v
retrieving revision 1.37
diff -u -p -r1.37 buildlink3.mk
--- buildlink3.mk	9 Sep 2019 12:22:03 -0000	1.37
+++ buildlink3.mk	11 Jul 2020 17:29:03 -0000
@@ -5,14 +5,24 @@ BUILDLINK_TREE+=	fontconfig
 .if !defined(FONTCONFIG_BUILDLINK3_MK)
 FONTCONFIG_BUILDLINK3_MK:=
 
+.if !defined(USE_BUILTIN.fontconfig)
+CHECK_BUILTIN.fontconfig:=	yes
+.  include "../../fonts/fontconfig/builtin.mk"
+CHECK_BUILTIN.fontconfig:=	no
+.endif
+
 BUILDLINK_API_DEPENDS.fontconfig+=	fontconfig>=2.11.91
 BUILDLINK_ABI_DEPENDS.fontconfig+=	fontconfig>=2.13.0
 BUILDLINK_PKGSRCDIR.fontconfig?=	../../fonts/fontconfig
 
+.  include "../../mk/bsd.fast.prefs.mk"
+
 .include "../../archivers/bzip2/buildlink3.mk"
 .include "../../devel/gettext-lib/buildlink3.mk"
 .include "../../devel/zlib/buildlink3.mk"
+.  if !empty(USE_BUILTIN.fontconfig:M[Nn][Oo]) && ${OPSYS} == "NetBSD"
 .include "../../devel/libuuid/buildlink3.mk"
+.  endif
 .include "../../graphics/freetype2/buildlink3.mk"
 .include "../../textproc/expat/buildlink3.mk"
 .endif # FONTCONFIG_BUILDLINK3_MK