Fix out-of-tree build.

Ths fixes out of tree build by making the libs directory to be
dependency of libs-all.

Not that the the lib and include directory are created as the side efect
of the AC_CONFIG_FILES() and hence don't need to be created in the
top-level Makefile.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Tested-by: Petr Vorel <pvorel@suse.cz>
diff --git a/Makefile b/Makefile
index bc6e9a3..170c2da 100644
--- a/Makefile
+++ b/Makefile
@@ -110,6 +110,11 @@
 ## Pattern based subtarget rules.
 lib-install: lib-all
 
+$(abs_top_builddir)/libs:
+	mkdir -m 00755 -p "$@"
+
+libs-all: $(abs_top_builddir)/libs
+
 $(MAKE_TARGETS) include-all lib-all libs-all:
 	$(MAKE) -C "$(subst -all,,$@)" \
 		-f "$(abs_top_srcdir)/$(subst -all,,$@)/Makefile" all