Makefile.am: Make libraries depend on .map files

Without this, an update to the .map file doesn't re-trigger a re-link of
the library.

Change-Id: If0ea6f41730a28b04562d45efa6ca376abaf3f6b
diff --git a/src/core/Makefile.am b/src/core/Makefile.am
index 7e24013..50c39d1 100644
--- a/src/core/Makefile.am
+++ b/src/core/Makefile.am
@@ -111,6 +111,8 @@
 	libosmocore.map \
 	$(NULL)
 
+EXTRA_libosmocore_la_DEPENDENCIES = libosmocore.map
+
 libosmocore_la_LDFLAGS = \
 	$(LTLDFLAGS_OSMOCORE) \
 	-version-info \