test/prefered: fix compiling problem

There is problem when running "make test/prefered":

"
  CCLD     test/prefered
/usr/bin/ld: ./.libs/libnuma.so: undefined reference to `find_first'
collect2: error: ld returned 1 exit status
make: *** [Makefile:979: test/prefered] Error 1
"
Fixing it by modifying Makefile and perfered.c

Signed-off-by: Feng Tang <feng.tang@intel.com>

Makefile.am

@@ -98,7 +98,7 @@ test_nodemap_LDADD = libnuma.la
 test_pagesize_SOURCES = test/pagesize.c
 test_pagesize_LDADD = libnuma.la
 
-test_prefered_SOURCES = test/prefered.c
+test_prefered_SOURCES = test/prefered.c util.c
 test_prefered_LDADD = libnuma.la
 
 test_randmap_SOURCES = test/randmap.c

test/prefered.c

@@ -10,6 +10,10 @@
 
 #define err(x) perror(x),exit(1)
 
+void usage(void)
+{
+}
+
 int main(void)
 {
 	int max = numa_max_node();