tools/pkg-config: Replace with pkgconf

pkgconf is a newer, actively maintained implementation of pkg-config that
supports more aspects of the pkg-config file specification and provides a
library interface that applications can use to incorporate intelligent
handling of pkg-config files into themselves (such as build file
generators, IDEs, and compilers). Through its pkg-config compatibility
interface (activated when it is run as "pkg-config"), it also can
completely replace the original implementation.

It is also lighterweight and does not require glib2, as pkg-config does.

On other distros, pkgconf is symlinked to pkg-config. For simplicity here,
it is renamed to pkg-config.real, as in the original package.

Initial results have been positive. As before, pkgconf works as long as
the pkg-config files point to the proper paths.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
[backported upstream fix for Meson]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

tools/pkgconf/Makefile

@@ -0,0 +1,33 @@
+#
+# Copyright (C) 2006-2016 OpenWrt.org
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=pkgconf
+PKG_VERSION:=1.6.3
+
+PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
+PKG_SOURCE_URL:=https://distfiles.dereferenced.org/pkgconf
+PKG_HASH:=61f0b31b0d5ea0e862b454a80c170f57bad47879c0c42bd8de89200ff62ea210
+
+HOST_BUILD_PARALLEL:=1
+
+include $(INCLUDE_DIR)/host-build.mk
+
+unexport PKG_CONFIG
+
+define Host/Install
+	$(MAKE) -C $(HOST_BUILD_DIR) install
+	mv $(STAGING_DIR_HOST)/bin/pkgconf $(STAGING_DIR_HOST)/bin/pkg-config.real
+	$(INSTALL_BIN) ./files/pkg-config $(STAGING_DIR_HOST)/bin/pkg-config
+endef
+
+define Host/Clean
+	-$(MAKE) -C $(HOST_BUILD_DIR) uninstall
+	$(call Host/Clean/Default)
+endef
+
+$(eval $(call HostBuild))