glsl: Reorganize backend code, remove unneeded [[maybe_unused]]

src/shader_recompiler/backend/glsl/emit_glsl_control_flow.cpp

@@ -0,0 +1,22 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <string_view>
+
+#include "shader_recompiler/backend/glsl/emit_context.h"
+#include "shader_recompiler/backend/glsl/emit_glsl_instructions.h"
+#include "shader_recompiler/exception.h"
+
+namespace Shader::Backend::GLSL {
+
+void EmitJoin(EmitContext&) {
+    throw NotImplementedException("Join shouldn't be emitted");
+}
+
+void EmitDemoteToHelperInvocation(EmitContext& ctx,
+                                  [[maybe_unused]] std::string_view continue_label) {
+    ctx.Add("discard;");
+}
+
+} // namespace Shader::Backend::GLSL