Enables generating Lua's pkg-config file.

http://lua-users.org/lists/lua-l/2015-03/msg00338.html

--- a/Makefile	2014-10-30 00:14:41.000000000 +0100
+++ b/Makefile	2015-03-26 18:54:37.678374827 +0100
@@ -14,6 +14,7 @@
 INSTALL_BIN= $(INSTALL_TOP)/bin
 INSTALL_INC= $(INSTALL_TOP)/include
 INSTALL_LIB= $(INSTALL_TOP)/lib
+INSTALL_PC= $(INSTALL_LIB)/pkgconfig
 INSTALL_MAN= $(INSTALL_TOP)/man/man1
 INSTALL_LMOD= $(INSTALL_TOP)/share/lua/$V
 INSTALL_CMOD= $(INSTALL_TOP)/lib/lua/$V
@@ -39,9 +40,12 @@
 PLATS= aix bsd c89 freebsd generic linux macosx mingw posix solaris

 # What to install.
-TO_BIN= lua luac
+INTERPRETER= lua
+COMPILER= luac
+TO_BIN= $(INTERPRETER) $(COMPILER)
 TO_INC= lua.h luaconf.h lualib.h lauxlib.h lua.hpp
 TO_LIB= liblua.a
+TO_PC=  lua-$(V).pc
 TO_MAN= lua.1 luac.1

 # Lua version and release.
@@ -51,23 +55,29 @@
 # Targets start here.
 all:	$(PLAT)

-$(PLATS) clean:
+$(PLATS):
 	cd src && $(MAKE) $@

+clean:
+	cd src && $(MAKE) $@
+	$(RM) $(TO_PC)
+
 test:	dummy
 	src/lua -v

-install: dummy
-	cd src && $(MKDIR) $(INSTALL_BIN) $(INSTALL_INC) $(INSTALL_LIB) $(INSTALL_MAN) $(INSTALL_LMOD) $(INSTALL_CMOD)
+install: dummy $(TO_PC)
+	cd src && $(MKDIR) $(INSTALL_BIN) $(INSTALL_INC) $(INSTALL_LIB) $(INSTALL_PC) $(INSTALL_MAN) $(INSTALL_LMOD) $(INSTALL_CMOD)
 	cd src && $(INSTALL_EXEC) $(TO_BIN) $(INSTALL_BIN)
 	cd src && $(INSTALL_DATA) $(TO_INC) $(INSTALL_INC)
 	cd src && $(INSTALL_DATA) $(TO_LIB) $(INSTALL_LIB)
+	cd src && $(INSTALL_DATA) ../$(TO_PC) $(INSTALL_PC)
 	cd doc && $(INSTALL_DATA) $(TO_MAN) $(INSTALL_MAN)

 uninstall:
 	cd src && cd $(INSTALL_BIN) && $(RM) $(TO_BIN)
 	cd src && cd $(INSTALL_INC) && $(RM) $(TO_INC)
 	cd src && cd $(INSTALL_LIB) && $(RM) $(TO_LIB)
+	cd src && cd $(INSTALL_PC)  && $(RM) $(TO_PC)
 	cd doc && cd $(INSTALL_MAN) && $(RM) $(TO_MAN)

 local:
@@ -90,11 +100,13 @@
 	@echo "TO_BIN= $(TO_BIN)"
 	@echo "TO_INC= $(TO_INC)"
 	@echo "TO_LIB= $(TO_LIB)"
+	@echo "TO_P<pre>
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2019 Julien Lepiller &lt;julien@lepiller.eu&gt;
;;; Copyright © 2019 Tobias Geerinckx-Rice &lt;me@tobias.gr&gt;
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see &lt;http://www.gnu.org/licenses/&gt;.

(define-module (gnu packages poedit)
  #:use-module ((guix licenses) #:prefix license:)
  #:use-module (gnu packages)
  #:use-module (guix packages)
  #:use-module (guix git-download)
  #:use-module (guix utils)
  #:use-module (guix build-system gnu)
  #:use-module (gnu packages autotools)
  #:use-module (gnu packages boost)
  #:use-module (gnu packages enchant)
  #:use-module (gnu packages gettext)
  #:use-module (gnu packages gtk)
  #:use-module (gnu packages icu4c)
  #:us