build: don't add systemd path the include search path

Our internal copy of systemd should not be in the search path.
Instead, let users only
  #include "systemd/nm-sd.h"
which then includes everything from systemd that we need.

We want to avoid to accidentally include anything from our
systemd-copy. Any user of that should only include "nm-sd.h",
which then includes everything that is needed further.

For example, "src/devices/wwan/nm-modem-manager.c" has
  #include <systemd/nm-daemon.h>
which in turn includes
  #include "_sd-common.h"
This works all correctly before, because #include "" will first
look in the directory where sd-daemon.h is. However, our mixing of
external systemd library and internal copy is rather dangerous.
Try to avoid it further by keeping the include paths clean.

src/Makefile.am

@@ -76,9 +76,6 @@ AM_CPPFLAGS = \
 	$(SYSTEMD_JOURNAL_CFLAGS) \
 	$(CODE_COVERAGE_CFLAGS) \
 	\
-	-I$(top_srcdir)/src/systemd/src/systemd/ \
-	-I$(top_srcdir)/src/systemd/ \
-	\
 	$(NULL)
 
 AM_LDFLAGS = $(CODE_COVERAGE_LDFLAGS)

src/devices/nm-device.c

@@ -62,8 +62,8 @@
 #include "nm-core-internal.h"
 #include "nm-default-route-manager.h"
 #include "nm-route-manager.h"
+#include "systemd/nm-sd.h"
 #include "nm-lldp-listener.h"
-#include "sd-ipv4ll.h"
 #include "nm-audit-manager.h"
 #include "nm-arping-manager.h"
 

src/devices/nm-lldp-listener.c

@@ -28,7 +28,7 @@
 #include "nm-platform.h"
 #include "nm-utils.h"
 
-#include "sd-lldp.h"
+#include "systemd/nm-sd.h"
 
 #define MAX_NEIGHBORS         4096
 #define MIN_UPDATE_INTERVAL_NS (2 * NM_UTILS_NS_PER_SECOND)

src/devices/tests/Makefile.am

@@ -5,9 +5,6 @@ AM_CPPFLAGS = \
 	-I$(top_builddir)/libnm-core \
 	-I$(top_srcdir)/src/platform \
 	-I$(top_srcdir)/src/devices \
-	-I$(top_srcdir)/src/systemd/ \
-	-I$(top_srcdir)/src/systemd/src/systemd/ \
-	-I$(top_srcdir)/src/systemd/src/libsystemd-network/ \
 	-I$(top_srcdir)/src \
 	-I$(top_builddir)/src \
 	-DG_LOG_DOMAIN=\""NetworkManager"\" \

src/devices/tests/test-lldp.c

@@ -27,9 +27,7 @@
 #include <sys/types.h>
 
 #include "nm-lldp-listener.h"
-#include "nm-sd.h"
-
-#include "sd-lldp.h"
+#include "systemd/nm-sd.h"
 
 #include "test-common.h"
 

src/dhcp-manager/nm-dhcp-systemd.c

@@ -34,10 +34,7 @@
 #include "NetworkManagerUtils.h"
 #include "nm-platform.h"
 #include "nm-dhcp-client-logging.h"
-#include "nm-sd.h"
-
-#include "sd-dhcp-client.h"
-#include "sd-dhcp6-client.h"
+#include "systemd/nm-sd.h"
 
 G_DEFINE_TYPE (NMDhcpSystemd, nm_dhcp_systemd, NM_TYPE_DHCP_CLIENT)
 

src/main.c

@@ -49,7 +49,7 @@
 #include "nm-auth-manager.h"
 #include "nm-core-internal.h"
 #include "nm-exported-object.h"
-#include "nm-sd.h"
+#include "systemd/nm-sd.h"
 
 #if !defined(NM_DIST_VERSION)
 # define NM_DIST_VERSION VERSION

src/nm-iface-helper.c

@@ -44,7 +44,7 @@ extern unsigned int if_nametoindex (const char *__ifname);
 #include "nm-lndp-rdisc.h"
 #include "nm-utils.h"
 #include "nm-setting-ip6-config.h"
-#include "nm-sd.h"
+#include "systemd/nm-sd.h"
 
 #if !defined(NM_DIST_VERSION)
 # define NM_DIST_VERSION VERSION

src/systemd/nm-sd.h

@@ -19,6 +19,13 @@
 #ifndef __NM_SD_H__
 #define __NM_SD_H__
 
+#include "systemd/src/systemd/sd-dhcp-client.h"
+#include "systemd/src/systemd/sd-dhcp6-client.h"
+#include "systemd/src/systemd/sd-lldp.h"
+#include "systemd/src/systemd/sd-ipv4ll.h"
+
+/*****************************************************************************/
+
 guint nm_sd_event_attach_default (void);
 
 /*****************************************************************************

src/tests/Makefile.am

@@ -123,8 +123,7 @@ test_wired_defname_LDADD = \
 test_systemd_CFLAGS = \
 	"-I$(srcdir)/../" \
 	"-I$(srcdir)/../platform" \
-	"-I$(srcdir)/../systemd" \
-	"-I$(srcdir)/../systemd/src/systemd"
+	$(NULL)
 
 test_systemd_SOURCES = \
 	test-systemd.c

src/tests/test-systemd.c

@@ -19,11 +19,7 @@
 
 #include "nm-default.h"
 
-#include "nm-sd.h"
-
-#include "sd-dhcp-client.h"
-#include "sd-lldp.h"
-#include "sd-event.h"
+#include "systemd/nm-sd.h"
 
 #include "nm-test-utils-core.h"