obs-studio-plugins.obs-ndi: use NDI SDK headers directly

obs-ndi bundles the NDI SDK headers to avoid a more complicated build
setup, but this plays against us here because the soversion for the v5
NDI SDK is "5" even though as far as I know it's fully ABI compatible
with the v4 headers in use here.

Work around the v4/v5 incompatibility here by using the upstream SDK
headers instead.

pkgs/applications/video/obs-studio/plugins/obs-ndi.nix

@@ -16,7 +16,15 @@ stdenv.mkDerivation rec {
 
   patches = [ ./fix-search-path.patch ./hardcode-ndi-path.patch ];
 
-  postPatch = "sed -i -e s,@NDI@,${ndi},g src/obs-ndi.cpp";
+  postPatch = ''
+    # Add path (variable added in hardcode-ndi-path.patch)
+    sed -i -e s,@NDI@,${ndi},g src/obs-ndi.cpp
+
+    # Replace bundled NDI SDK with the upstream version
+    # (This fixes soname issues)
+    rm -rf lib/ndi
+    ln -s ${ndi}/include lib/ndi
+  '';
 
   cmakeFlags = [
     "-DLIBOBS_INCLUDE_DIR=${obs-studio}/include/obs"