pkgconfig: install a liburing.pc file

pkg-config (https://pkgconfig.freedesktop.org/) makes it easier to build
applications that have library dependencies.  Libraries ship .pc files
containing the compiler and linker flags needed to build successfully.
This saves applications from hardcoding these details into their build
scripts, especially when these details can change between operating
systems or distributions.

To build a liburing application:

  gcc $(pkg-config --cflags --libs liburing) -o myapp myapp.c

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

.gitignore

@@ -12,3 +12,5 @@
 config-host.h
 config-host.mak
 config.log
+
+liburing.pc

Makefile

@@ -33,13 +33,22 @@ ifneq ($(MAKECMDGOALS),clean)
 include config-host.mak
 endif
 
-install:
+%.pc: %.pc.in
+	sed -e "s%@prefix@%$(prefix)%g" \
+	    -e "s%@libdir@%$(libdir)%g" \
+	    -e "s%@includedir@%$(includedir)%g" \
+	    -e "s%@NAME@%$(NAME)%g" \
+	    -e "s%@VERSION@%$(VERSION)%g" \
+	    $< >$@
+
+install: $(NAME).pc
 	@$(MAKE) -C src install prefix=$(DESTDIR)$(prefix) includedir=$(DESTDIR)$(includedir) libdir=$(DESTDIR)$(libdir)
+	$(INSTALL) -D -m 644 $(NAME).pc $(DESTDIR)$(libdir)/pkgconfig/$(NAME).pc
 	$(INSTALL) -m 755 -d $(DESTDIR)$(mandir)/man2
 	$(INSTALL) -m 644 man/*.2 $(DESTDIR)$(mandir)/man2
 
 clean:
-	@rm -f config-host.mak config-host.h cscope.out
+	@rm -f config-host.mak config-host.h cscope.out $(NAME).pc
 	@$(MAKE) -C src clean
 	@$(MAKE) -C test clean
 	@$(MAKE) -C examples clean

liburing.pc.in

@@ -0,0 +1,12 @@
+prefix=@prefix@
+exec_prefix=${prefix}
+libdir=@libdir@
+includedir=@includedir@
+
+Name: @NAME@
+Version: @VERSION@
+Description: io_uring library
+URL: http://git.kernel.dk/cgit/liburing/
+
+Libs: -L${libdir} -luring
+Cflags: -I${includedir}