Consistenly format variables in */Makefile.am files

Change-Id: Ifa21513c007072314097b7bec188579972dc1694
diff --git a/openbsc/tests/gsm0408/Makefile.am b/openbsc/tests/gsm0408/Makefile.am
index 79fb9f1..11fa6b9 100644
--- a/openbsc/tests/gsm0408/Makefile.am
+++ b/openbsc/tests/gsm0408/Makefile.am
@@ -1,12 +1,34 @@
-AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include
-AM_CFLAGS=-Wall $(LIBOSMOCORE_CFLAGS) $(LIBOSMOGSM_CFLAGS) $(LIBOSMOABIS_CFLAGS)
-noinst_PROGRAMS = gsm0408_test
+AM_CPPFLAGS = \
+	$(all_includes) \
+	-I$(top_srcdir)/include \
+	$(NULL)
 
-EXTRA_DIST = gsm0408_test.ok
+AM_CFLAGS = \
+	-Wall \
+	$(LIBOSMOCORE_CFLAGS) \
+	$(LIBOSMOGSM_CFLAGS) \
+	$(LIBOSMOABIS_CFLAGS) \
+	$(NULL)
 
-gsm0408_test_SOURCES = gsm0408_test.c
-gsm0408_test_LDADD =	$(top_builddir)/src/libbsc/libbsc.a \
-			$(top_builddir)/src/libmsc/libmsc.a \
-			$(top_builddir)/src/libtrau/libtrau.a \
-			$(top_builddir)/src/libcommon/libcommon.a \
-			$(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOABIS_LIBS) -ldbi
+noinst_PROGRAMS = \
+	gsm0408_test \
+	$(NULL)
+
+EXTRA_DIST = \
+	gsm0408_test.ok \
+	$(NULL)
+
+gsm0408_test_SOURCES = \
+	gsm0408_test.c \
+	$(NULL)
+
+gsm0408_test_LDADD = \
+	$(top_builddir)/src/libbsc/libbsc.a \
+	$(top_builddir)/src/libmsc/libmsc.a \
+	$(top_builddir)/src/libtrau/libtrau.a \
+	$(top_builddir)/src/libcommon/libcommon.a \
+	$(LIBOSMOCORE_LIBS) \
+	$(LIBOSMOGSM_LIBS) \
+	$(LIBOSMOABIS_LIBS) \
+	-ldbi \
+	$(NULL)