fix two mistakes in AM_LDFLAGS
diff --git a/openbsc/src/libgb/Makefile.am b/openbsc/src/libgb/Makefile.am
index cb656cc..eebd76c 100644
--- a/openbsc/src/libgb/Makefile.am
+++ b/openbsc/src/libgb/Makefile.am
@@ -1,6 +1,6 @@
 INCLUDES = $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)
 AM_CFLAGS=-Wall -fno-strict-aliasing $(LIBOSMOCORE_CFLAGS) $(LIBOSMOVTY_CFLAGS) $(COVERAGE_CFLAGS)
-AM_LDFLAGS = $(LIBOSMOCORE_LIBS) $(LIBOSMOCORE_GSM) $(LIBOSMOVTY_LIBS) $(COVERAGE_LDFLAGS)
+AM_LDFLAGS = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOVTY_LIBS) $(COVERAGE_LDFLAGS)
 
 noinst_LIBRARIES = libgb.a