Make examples optional

Add --enable-examples configure switch which allows to disable the
compilation and installation of the examples.
Default is off.

configure.ac

@@ -414,6 +414,11 @@ if test "x$enable_introspection" = xyes; then
 fi
 AM_CONDITIONAL([ENABLE_INTROSPECTION], [test "x$enable_introspection" = xyes])
 
+AC_ARG_ENABLE([examples],
+              AS_HELP_STRING([--enable-examples], [Build the example programs]),,
+              [enable_examples=no])
+
+AM_CONDITIONAL(BUILD_EXAMPLES, test "x$enable_examples" = "xyes")
 
 # ********************
 # Internationalization

src/Makefile.am

 
-SUBDIRS = polkit polkitbackend polkitagent polkitd nullbackend programs examples
+SUBDIRS = polkit polkitbackend polkitagent polkitd nullbackend programs
+
+if BUILD_EXAMPLES
+SUBDIRS += examples
+endif
 
 clean-local :
 	rm -f *~