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_PC= $(TO_PC)"
 	@echo "TO_MAN= $(TO_MAN)"
 	@echo "INSTALL_TOP= $(INSTALL_TOP)"
 	@echo "INSTALL_BIN= $(INSTALL_BIN)"
 	@echo "INSTALL_INC= $(INSTALL_INC)"
 	@echo "INSTALL_LIB= $(INSTALL_LIB)"
+	@echo "INSTALL_PC= $(INSTALL_PC)"
 	@echo "INSTALL_MAN= $(INSTALL_MAN)"
 	@echo "INSTALL_LMOD= $(INSTALL_LMOD)"
 	@echo "INSTALL_CMOD= $(INSTALL_CMOD)"
@@ -103,12 +115,28 @@

 # echo pkg-config data
 pc:
-	@echo "version=$R"
-	@echo "prefix=$(INSTALL_TOP)"
-	@echo "libdir=$(INSTALL_LIB)"
-	@echo "includedir=$(INSTALL_INC)"
+	@echo 'prefix=$(INSTALL_TOP)'
+	@echo 'libdir=$(INSTALL_LIB)'
+	@echo 'includedir=$(INSTALL_INC)'
+	@echo 'bindir=$(INSTALL_BIN)'
+	@echo
+	@echo 'INSTALL_LMOD=$(INSTALL_LMOD)'
+	@echo 'INSTALL_CMOD=$(INSTALL_CMOD)'
+	@echo 'INTERPRETER=$${bindir}/$(INTERPRETER)'
+	@echo 'COMPILER=$${bindir}/$(COMPILER)'
+	@echo
+	@echo 'Name: Lua'
+	@echo 'Description: A powerful, fast, lightweight, embeddable scripting language'
+	@echo 'Version: $(R)'
+	@echo
+	@echo 'Libs: -L$${libdir} -llua -lm'
+	@echo 'Cflags: -I$${includedir}'
+
+pkg-config: $(TO_PC)
+$(TO_PC):
+	@$(MAKE) -s pc > $@

 # list targets that do not create files (but not all makes understand .PHONY)
-.PHONY: all $(PLATS) clean test install local none dummy echo pecho lecho
+.PHONY: all $(PLATS) clean test install local none dummy echo pecho lecho pkg-config

 # (end of Makefile)