Allow glslang global lock to be used during process teardown

* During capture we may have to shutdown glslang from inside a global
  destructor, we need to ensure the lock is still valid.

renderdoc/3rdparty/glslang/glslang/MachineIndependent/ShaderLang.cpp

@@ -83,7 +83,11 @@ int NumberOfClients = 0;
 
 // global initialization lock
 #ifndef DISABLE_THREAD_SUPPORT
-std::mutex init_lock;
+std::mutex &init_lock()
+{
+  std::mutex *lock = new std::mutex;
+  return *lock;
+}
 #endif
 
 
@@ -430,7 +434,7 @@ bool SetupBuiltinSymbolTable(int version, EProfile profile, const SpvVersion& sp
 
     // Make sure only one thread tries to do this at a time
 #ifndef DISABLE_THREAD_SUPPORT
-    const std::lock_guard<std::mutex> lock(init_lock);
+    const std::lock_guard<std::mutex> lock(init_lock());
 #endif
 
     // See if it's already been done for this version/profile combination
@@ -1333,7 +1337,7 @@ bool CompileDeferred(
 int ShInitialize()
 {
 #ifndef DISABLE_THREAD_SUPPORT
-    const std::lock_guard<std::mutex> lock(init_lock);
+    const std::lock_guard<std::mutex> lock(init_lock());
 #endif
     ++NumberOfClients;
 
@@ -1390,7 +1394,7 @@ void ShDestruct(ShHandle handle)
 int ShFinalize()
 {
 #ifndef DISABLE_THREAD_SUPPORT
-    const std::lock_guard<std::mutex> lock(init_lock);
+    const std::lock_guard<std::mutex> lock(init_lock());
 #endif
     --NumberOfClients;
     assert(NumberOfClients >= 0);