switch, uwp, libretro build fixes

core/oslib/oslib.cpp

@@ -199,7 +199,7 @@ void saveScreenshot(const std::string& name, const std::vector<u8>& data)
 		StorageFolder^ folder = KnownFolders::PicturesLibrary;	// or SavedPictures?
 		if (folder == nullptr) {
 			INFO_LOG(COMMON, "KnownFolders::PicturesLibrary is null");
-			throw FlycastException();
+			throw FlycastException("Can't find Pictures library");
 		}
 		nowide::wstackstring wstr;
 		wchar_t *wname = wstr.convert(name.c_str());
@@ -220,7 +220,7 @@ void saveScreenshot(const std::string& name, const std::vector<u8>& data)
 	}
 	catch (COMException^ e) {
 		WARN_LOG(COMMON, "Save screenshot failed: %S", e->Message->Data());
-		throw FlycastException();
+		throw FlycastException("");
 	}
 }
 

core/rend/dx11/dx11_renderer.cpp

@@ -1384,8 +1384,12 @@ bool DX11Renderer::GetLastFrame(std::vector<u8>& data, int& width, int& height)
 
 	quad->draw(fbTextureView, samplers->getSampler(true), nullptr, -1.f, -1.f, 2.f, 2.f, config::Rotate90);
 
+#ifndef LIBRETRO
 	deviceContext->OMSetRenderTargets(1, &theDX11Context.getRenderTarget().get(), nullptr);
-
+#else
+	ID3D11RenderTargetView *nullView = nullptr;
+	deviceContext->OMSetRenderTargets(1, &nullView, nullptr);
+#endif
 	D3D11_TEXTURE2D_DESC desc;
 	dstTex->GetDesc(&desc);
 	desc.Usage = D3D11_USAGE_STAGING;

shell/switch/switch_main.cpp

@@ -21,6 +21,8 @@
 #include "emulator.h"
 #include "ui/mainui.h"
 #include "oslib/directory.h"
+#include <vector>
+#include <string>
 
 int main(int argc, char *argv[])
 {
@@ -58,4 +60,13 @@ void os_DoEvents()
 {
 }
 
+namespace hostfs
+{
+
+void saveScreenshot(const std::string& name, const std::vector<u8>& data)
+{
+	throw FlycastException("Not supported on Switch");
+}
+
+}
 #endif	//!LIBRETRO