[lsan] Deflake fork_and_leak test

Author: vitalybuka

compiler-rt/test/lsan/TestCases/Linux/fork_and_leak.cpp

@@ -18,7 +18,8 @@ int main() {
     assert(WIFEXITED(status));
     return WEXITSTATUS(status);
   } else {
-    malloc(1337);
+    for (int i = 0; i < 10; ++i)
+      malloc(1337);
     // CHECK: LeakSanitizer: detected memory leaks
   }
   return 0;