[libunwind] undef NDEBUG for assert.h in tests.

This makes sure the assertions also get verified in optimized builds.
This matches what is already done in bad_unwind_info.pass.cpp.

Reviewed By: #libunwind, MaskRay

Differential Revision: https://reviews.llvm.org/D131210

NOKEYCHECK=True
GitOrigin-RevId: fc6a6ee507ec2df0df7d34ba19feccb776297e4c
diff --git a/test/libunwind_02.pass.cpp b/test/libunwind_02.pass.cpp
index c0d6b05..fc03437 100644
--- a/test/libunwind_02.pass.cpp
+++ b/test/libunwind_02.pass.cpp
@@ -10,6 +10,7 @@
 // TODO: Figure out why this fails with Memory Sanitizer.
 // XFAIL: msan
 
+#undef NDEBUG
 #include <assert.h>
 #include <stdlib.h>
 #include <unwind.h>