CI mac: add /Library/Framework to rpath

needed for DELTACAST, otherwise manpage generation fails with:
```
 dyld[40232]: Library not loaded: @rpath/VideoMasterHD.framework/Versions/A/VideoMasterHD
  Referenced from: <3D8A8CBA-1094-3538-9770-331DE9A2D6D2> /Users/runner/work/UltraGrid/UltraGrid/bin/uv
  Reason: tried: '/usr/local/lib/VideoMasterHD.framework/Versions/A/VideoMasterHD' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/usr/local/lib/VideoMasterHD.framework/Versions/A/VideoMasterHD' (no such file), '/usr/local/lib/VideoMasterHD.framework/Versions/A/VideoMasterHD' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/usr/local/lib/VideoMasterHD.framework/Versions/A/VideoMasterHD' (no such file)
Could not obtain data from UG/reflector output!
```

.github/scripts/macOS/prepare.sh

@@ -14,8 +14,9 @@ if [ -z "${GITHUB_ENV-}" ]; then
 fi
 
 export CPATH=/usr/local/include
-export DYLIBBUNDLER_FLAGS="${DYLIBBUNDLER_FLAGS:+$DYLIBBUNDLER_FLAGS }-s /usr/local/lib"
-export LDFLAGS="-Wl,-rpath,/usr/local/lib"
+export DYLIBBUNDLER_FLAGS="${DYLIBBUNDLER_FLAGS:+$DYLIBBUNDLER_FLAGS }\
+ -s /usr/local/lib -s /Library/Frameworks"
+export LDFLAGS="-Wl,-rpath,/usr/local/lib -Wl,-rpath,/Library/Frameworks"
 export LIBRARY_PATH=/usr/local/lib
 if [ "$(uname -m)" = arm64 ]; then
         CPATH=/usr/local/include:/opt/homebrew/include