Add missing include

Summary:
`std::runtime_error` is defined in this header. Most build
systems seem to end up including it transitively anyways, but one version
of Clang on my Mac does not.

Test Plan:
`fbconfig -r folly && fbmake dbg` still works. Builds on my
Mac with MacPorts clang 3.6.

Reviewed By: ldbrandy@fb.com

Subscribers: folly-diffs@, yfeldblum, chalfant

FB internal diff: D2127268

Signature: t1:2127268:1433437985:546d0de71d8973d10f8ae3fdb6c61efae59444b9

diff --git a/folly/Executor.h b/folly/Executor.h
index c790045985885558b4b13c79995663ee825f33f7..2af0b809c27059ea48f3e06d92dd0c30c97bb0c0 100644 (file)
--- a/folly/Executor.h
+++ b/folly/Executor.h
@@ -19,6 +19,7 @@
 #include <atomic>
 #include <climits>
 #include <functional>
+#include <stdexcept>
 
 namespace folly {