use pkg-config variables instead of hardcoded paths

.gitignore

@@ -2,26 +2,23 @@
 */*~
 *.o
 *.pdf
-cups
 .vscode/
 .gdb_history
 gmon.out
-Makefile.in
 .gitignore
 aclocal.m4
-Makefile
-*/Makefile
-depcomp
-install-sh
-missing
 aclocal.*
-compile
-autom4*
+autom4te.cache/
+build-aux/
+configure
 config.guess
 config.sub
 config.log
 config.status
-configure
-data/org.openprinting.Backend.CUPS.service
+Makefile
+Makefile.in
 src/.deps
+src/cups
+data/org.openprinting.Backend.CUPS.service
 tmp/
+*/Makefile

autogen.sh

@@ -1,5 +1,6 @@
 #! /bin/sh
 
-aclocal \
+mkdir -p build-aux \
+&& aclocal \
 && automake --add-missing \
 && autoconf

configure.ac

@@ -3,15 +3,16 @@
 
 AC_PREREQ([2.69])
 AC_INIT([cpdb-backend-cups], [2.0b1], [https://github.com/OpenPrinting/cpdb-backend-cups/issues/], [cpdb-backend-cups], [https://github.com/OpenPrinting/cpdb-backend-cups])
-AM_INIT_AUTOMAKE([-Wall foreign])
+AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_SRCDIR([src/print_backend_cups.c])
+AM_INIT_AUTOMAKE([-Wall foreign])
 
 : ${CFLAGS=""}
 # Check for a C compiler
 AC_PROG_CC
 
 
-# Checks for backend library
+# Checks for backend library 
 PKG_CHECK_MODULES([CPDB],[cpdb >= 2])
 PKG_CHECK_MODULES([GIO],[gio-2.0])
 PKG_CHECK_MODULES([GIOUNIX],[gio-unix-2.0])
@@ -27,15 +28,28 @@ AC_TYPE_SIZE_T
 AC_FUNC_MALLOC
 
 # The Dbus service directory
-DBUS_SERVICES_DIR="/usr/share/dbus-1/services"
-AC_SUBST(DBUS_SERVICES_DIR)
+AC_MSG_CHECKING([dbus service file path])
+PKG_CHECK_VAR([DBUS_SERVICES_DIR], [dbus-1], [session_bus_services_dir],
+  AC_MSG_RESULT($DBUS_SERVICES_DIR),
+  AC_MSG_FAILURE([cannot locate session_bus_services_dir])
+)
 
 # The info directory which will be read by the frontend
-INFO_DIR="/usr/share/print-backends"
-AC_SUBST(INFO_DIR)
+AC_MSG_CHECKING([CPDB backend info path])
+PKG_CHECK_VAR([INFO_DIR], [cpdb], [cpdb_backend_info_dir],
+  AC_MSG_RESULT($INFO_DIR),
+  AC_MSG_FAILURE([cannot locate cpdb_backend_info_dir])
+)
 
 # The directory for the backend executables
-CPDB_BACKEND_DIR="$libdir/print-backends"
-AC_SUBST(CPDB_BACKEND_DIR)
+AC_MSG_CHECKING([CPDB backend executables path])
+PKG_CHECK_VAR([CPDB_BACKEND_DIR], [cpdb], [cpdb_backend_exec_dir],
+  AC_MSG_RESULT($CPDB_BACKEND_DIR),
+  AC_MSG_FAILURE([cannot locate cpdb_backend_exec_dir])
+)
+
+AC_CONFIG_FILES([Makefile
+                 src/Makefile
+                 data/Makefile])
 
-AC_OUTPUT([Makefile src/Makefile data/Makefile])
+AC_OUTPUT