I’m falling the bellow mentioned link to use vcpkg package manager in manifest mode.
https://learn.microsoft.com/en-us/vcpkg/get_started/get-started-vs?pivots=shell-cmd
In the CMakeUserPresets.json I’m getting the bellow mentioned error.
I also tried providing the absolute path to my vcpkg.cmake file.

I’ve created environment variable VCPKG_ROOT=C:vcpkg

CMakeUserPresets.json

{
  "version": 2,
  "configurePresets": [
    {
      "name": "default",
      "generator": "Ninja",
      "binaryDir": "${sourceDir}/build",
      "cacheVariables": {
        "CMAKE_TOOLCHAIN_FILE": "$env{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake"
        //"CMAKE_TOOLCHAIN_FILE": "c:\vcpkg\scripts\buildsystems\vcpkg.cmake"
      }
    }
  ]
}

CMake Output

1> CMake generation started for configuration: 'default'.
1> Illegal characters in path.
Illegal characters in path.
   at System.IO.Path.CheckInvalidPathChars(String path, Boolean checkAdditional)
   at System.IO.Path.Combine(String path1, String path2)
   at libcmake.RelativePathStringComparer.GetCanonicalPath(String path)
   at libcmake.RelativePathStringComparer.Equals(String x, String y)
   at libcmake.CMakeDaemonDriver.HasToolchainChanged(CMakeCommandLine cmdLine, String currentToolchain, List`1 messages, IEqualityComparer`1 comparer)
   at libcmake.CMakeDaemonDriver.<DeleteCacheIfConsistencyCheckFailsAsync>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at libcmake.CMakeListsParser.<SetAndCheckToolchainAsync>d__39.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at libcmake.CMakeListsParser.<ParseImplAsync>d__40.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at libcmake.CMakeListsParser.<ParseAsync>d__36.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.CMake.Project.ExternalBuildProject.ProjectProvider.<ParseProjectAsync>d__46.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.VisualStudio.CMake.Project.ExternalBuildProject.ProjectProvider.<ParseProjectAsync>d__46.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Workspace.ExternalBuildFramework.Impl.ParseCache.<ParseAsyncImpl>d__34.MoveNext()