Require explicit debug information to support source debugging

* SPIR-V files currently can have source files, but not source debugging
  information, which is a distinction that didn't exist otherwise.

qrenderdoc/Windows/ShaderViewer.cpp

@@ -542,10 +542,10 @@ void ShaderViewer::debugShader(const ShaderBindpointMapping *bind, const ShaderR
       ui->floatView->hide();
     }
 
-    if(m_ShaderDetails->debugInfo.files.isEmpty())
+    if(!m_ShaderDetails->debugInfo.sourceDebugInformation)
     {
       ui->debugToggle->setEnabled(false);
-      ui->debugToggle->setText(tr("Source Unavailable"));
+      ui->debugToggle->setText(tr("Source debugging Unavailable"));
     }
 
     ui->debugVars->setColumns({tr("Name"), tr("Value")});

renderdoc/api/replay/shader_types.h

@@ -1298,6 +1298,10 @@ functionality
 )");
   bool debuggable = true;
 
+  DOCUMENT(R"(Indicates whether this shader has debug information to allow source-level debugging.
+)");
+  bool sourceDebugInformation = false;
+
   DOCUMENT(R"(If :data:`debuggable` is false then this contains a simple explanation of why the
 shader is not supported for debugging
 )");

renderdoc/driver/shaders/dxbc/dxbc_reflect.cpp

@@ -247,6 +247,8 @@ void MakeShaderReflection(DXBC::DXBCContainer *dxbc, ShaderReflection *refl,
 
     refl->debugInfo.encoding = ShaderEncoding::HLSL;
 
+    refl->debugInfo.sourceDebugInformation = true;
+
     refl->debugInfo.compileFlags = dxbc->GetDebugInfo()->GetShaderCompileFlags();
 
     refl->debugInfo.files.resize(dxbc->GetDebugInfo()->Files.size());