[ASan] Add aligned_alloc declaration to aligned_alloc-alignment.cc test.

aligned_alloc is not always defined in headers.

Differential Revision: https://reviews.llvm.org/D44404

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@328726 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/asan/TestCases/Linux/aligned_alloc-alignment.cc b/test/asan/TestCases/Linux/aligned_alloc-alignment.cc
index 618aa8a..5483c76 100644
--- a/test/asan/TestCases/Linux/aligned_alloc-alignment.cc
+++ b/test/asan/TestCases/Linux/aligned_alloc-alignment.cc
@@ -5,6 +5,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+extern void *aligned_alloc (size_t alignment, size_t size);
+
 int main() {
   void *p = aligned_alloc(17, 100);
   // CHECK: ERROR: AddressSanitizer: invalid allocation alignment: 17