SourceKitLSP: normalise paths for clangd

Ensure that we use the native path representation for clangd rather than
the POSIX spelling.  This is required to map the command for the source
file.

Author: compnerd

Sources/SourceKitLSP/Clang/ClangLanguageServer.swift

@@ -420,7 +420,7 @@ extension ClangLanguageServerShim {
     if let compileCommand = clangBuildSettings?.compileCommand {
       let note = DidChangeConfigurationNotification(settings: .clangd(
         ClangWorkspaceSettings(
-          compilationDatabaseChanges: [url.path: compileCommand])))
+          compilationDatabaseChanges: [AbsolutePath(url.path).pathString: compileCommand])))
       forwardNotificationToClangdOnQueue(note)
     }
   }