cmake/ui : refactor the build (#23352)

tools/ui/svelte.config.js

@@ -2,6 +2,10 @@ import { mdsvex } from 'mdsvex';
 import adapter from '@sveltejs/adapter-static';
 import { vitePreprocess } from '@sveltejs/vite-plugin-svelte';
 
+// CMake sets LLAMA_UI_OUT_DIR to the staging dir under the build tree; manual
+// `npm run build` runs without the env var default to ./dist.
+const outDir = process.env.LLAMA_UI_OUT_DIR ?? './dist';
+
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
 	// Consult https://svelte.dev/docs/kit/integrations
@@ -14,8 +18,8 @@ const config = {
 		},
 		router: { type: 'hash' },
 		adapter: adapter({
-			pages: '../../build/tools/ui/dist',
-			assets: '../../build/tools/ui/dist',
+			pages: outDir,
+			assets: outDir,
 			fallback: 'index.html',
 			precompress: false,
 			strict: true