Placate unused variable warnings uncovered by improvements to clang's -Wunused-variable

llvm-svn: 315809
diff --git a/libcxx/test/std/depr/depr.c.headers/complex.h.pass.cpp b/libcxx/test/std/depr/depr.c.headers/complex.h.pass.cpp
index 0e3fd3e..4effd96 100644
--- a/libcxx/test/std/depr/depr.c.headers/complex.h.pass.cpp
+++ b/libcxx/test/std/depr/depr.c.headers/complex.h.pass.cpp
@@ -14,4 +14,5 @@
 int main()
 {
     std::complex<double> d;
+    (void)d;
 }