libgsmhr: Fix parallel build dependency

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/libgsmhr/Makefile.am b/libgsmhr/Makefile.am
index 9d6a9fc..df12c53 100644
--- a/libgsmhr/Makefile.am
+++ b/libgsmhr/Makefile.am
@@ -16,7 +16,7 @@
 	sed -i -e"s/long int/int/" -e"s/long/int/" "${REFSRC_PATH}/typedefs.h"
 	touch $@
 
-${REFSRC_PATH}/*.c: ${REFSRC_PATH}/.downloaded
+$(REFSRC_SRC) libgsmhr.c: ${REFSRC_PATH}/.downloaded
 
 lib_LTLIBRARIES = libgsmhr.la
 libgsmhr_la_SOURCES = $(REFSRC_SRC) libgsmhr.c