Fix build when disable thread support.

Patch by Howard Su.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73680 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/RWMutex.cpp b/lib/System/RWMutex.cpp
index 6cf2076..2b6cf6c 100644
--- a/lib/System/RWMutex.cpp
+++ b/lib/System/RWMutex.cpp
@@ -23,7 +23,7 @@
 // Define all methods as no-ops if threading is explicitly disabled
 namespace llvm {
 using namespace sys;
-RWMutex::RWMutex( bool recursive) { }
+RWMutex::RWMutex() { }
 RWMutex::~RWMutex() { }
 bool RWMutex::reader_acquire() { return true; }
 bool RWMutex::reader_release() { return true; }