TT#124273 Fix building arch:all packages

Switch from the unconditional installation of the xtables module to
do that through debhelper fragment files. This makes sure we only do
that whenever we are building these packages, and thus do not fail
to install into a non-existent directory.

Change-Id: Ib7d96a9636435d030c42f265214cc1546e373699

debian/ngcp-rtpengine-iptables.dirs

@@ -0,0 +1 @@
+${env:XTABLES_DIR}

debian/ngcp-rtpengine-iptables.install

@@ -0,0 +1 @@
+iptables-extension/libxt_RTPENGINE.so ${env:XTABLES_DIR}

debian/rules

@@ -15,7 +15,7 @@ sname:=ngcp-rtpengine
 sversion:=$(DEB_VERSION_UPSTREAM)
 ## end of kernel package specific stuff
 
-XTABLES_DIR:=$(shell pkg-config xtables --variable=xtlibdir || echo /lib/xtables)
+export XTABLES_DIR := $(shell pkg-config xtables --variable=xtlibdir || echo /lib/xtables)
 
 ifneq (,$(filter $(DEB_BUILD_PROFILES),pkg.ngcp-rtpengine.no-transcoding))
 export with_transcoding = no
@@ -44,9 +44,5 @@ execute_before_dh_auto_install-indep:
 	markdown README.md | gzip -9 > debian/README.html.gz
 	gzip -9 < README.md > debian/README.md.gz
 
-execute_after_dh_install:
-	dh_installdirs -pngcp-rtpengine-iptables $(XTABLES_DIR)
-	install -m 0644 iptables-extension/libxt_RTPENGINE.so debian/ngcp-rtpengine-iptables/$(XTABLES_DIR)
-
 execute_after_dh_installsystemd:
 	dh_installsystemd -pngcp-rtpengine-recording-daemon --name=ngcp-rtpengine-recording-nfs-mount