Fix LLVM GHA builds as best I can for now

.github/workflows/cmake.yml

@@ -217,7 +217,7 @@ jobs:
 
       - name: Setup NuGet Credentials
         run: >
-          & (C:/vcpkg/vcpkg fetch nuget | tail -n 2)
+          & (C:/vcpkg/vcpkg --vcpkg-root "${{ env.VCPKG_ROOT }}" fetch nuget | tail -n 2)
           sources add
           -source "https://nuget.pkg.github.com/86Box/index.json"
           -storepasswordincleartext

vcpkg.json

@@ -9,7 +9,8 @@
         "libpng",
         "sdl2",
         "rtmidi",
-        "libslirp"
+        "libslirp",
+        "fluidsynth"
     ],
     "features": {
         "qt-ui": {