provide ~future_error() definition

llvm-svn: 134663
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 3aa229f7dca58676e2a4f143387fb0b53e2b783d
diff --git a/src/future.cpp b/src/future.cpp
index 98c7805..4c3a3fa 100644
--- a/src/future.cpp
+++ b/src/future.cpp
@@ -59,6 +59,10 @@
 {
 }
 
+future_error::~future_error() _NOEXCEPT
+{
+}
+
 void
 __assoc_sub_state::__on_zero_shared() _NOEXCEPT
 {