update malloc(0) check to handle expected behavior based upon config options

test/malloc/tst-mcheck.c

@@ -20,6 +20,7 @@
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <features.h>
 
 static int errors = 0;
 
@@ -53,7 +54,11 @@ main (void)
     merror ("realloc (p, 0) failed.");
 
   p = malloc (0);
+#if !defined(__UCLIBC__) || defined(__MALLOC_GLIBC_COMPAT__)
   if (p == NULL)
+#else
+  if (p != NULL)
+#endif
     merror ("malloc (0) failed.");
 
   p = realloc (p, 0);