pkg/54007: x11/xkbcomp needs a buildlink3.mk for meson to find it via pkgconfig

[davshao%gmail.com@localhost]

>Number:         54007
>Category:       pkg
>Synopsis:       x11/xkbcomp needs a buildlink3.mk for meson to find it via pkgconfig
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 23 05:55:00 +0000 2019
>Originator:     David Shao
>Release:        pkgsrc current
>Organization:
>Environment:
NetBSD xxxxxx.xxx 8.99.34 NetBSD 8.99.34 (GENERIC) #13: Thu Feb 21 21:41:43 PST 2019  xxxxxx%xxxxxx.xxx@localhost:/usr/obj/sys/arch/amd64/compile/GENERIC amd64
>Description:
Using a meson build on modular-xorg-server git current fails with

Dependency libsystemd-daemon found: NO (tried pkgconfig and cmake)

meson.build:110:4: ERROR:  'xkbcomp' is not a pkgconfig dependency

meson really likes to use pkgconfig to find things, and xkbcomp does have a generated xkbcomp.pc file.
>How-To-Repeat:

>Fix:
Add a buildlink3.mk.  I have no idea if the API_DEPENDS makes sense.

# $NetBSD$

BUILDLINK_TREE+=	xkbcomp

.if !defined(XKBCOMP_BUILDLINK3_MK)
XKBCOMP_BUILDLINK3_MK:=

BUILDLINK_API_DEPENDS.xkbcomp+=	xkbcomp>=1.4.2
BUILDLINK_PKGSRCDIR.xkbcomp?=	../../x11/xkbcomp
.endif # XKBCOMP_BUILDLINK3_MK

BUILDLINK_TREE+=	-xkbcomp