Fix FreeBSD build after r231145

llvm-svn: 231157
diff --git a/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp b/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp
index 493f36c..cce7a1e 100644
--- a/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp
+++ b/lldb/source/Plugins/Process/FreeBSD/FreeBSDThread.cpp
@@ -11,6 +11,7 @@
 // C++ Includes
 // Other libraries and framework includes
 #include "lldb/Core/State.h"
+#include "lldb/Target/UnixSignals.h"
 
 // Project includes
 #include "FreeBSDThread.h"