Build/Test Tools: Use --fast flag for Gutenberg builds.

Adds the `--fast` flag to Gutenberg build commands, which skips TypeScript-related steps (version validation, `tsc --build`, and type declaration file checks) that aren't needed when building for WordPress Core. These steps only produce `.d.ts` files which aren't shipped with Core. Also updates the Gutenberg ref to include the commit that adds `--fast` flag support.

The build times are now comparable to the build times we had using the npm packages.

Props dmsnell, johnbillion.
See #64393.


git-svn-id: https://develop.svn.wordpress.org/trunk@61450 602fd350-edb4-49c9-b593-d223f7449a82

Author: youknowriad

package.json

@@ -7,7 +7,7 @@
 		"url": "https://develop.svn.wordpress.org/trunk"
 	},
 	"gutenberg": {
-		"ref": "dea73b609a80016eb1cf3893ea183fe106a06740"
+		"ref": "892bfad51d2261f44f3a21f934b1c72bd29a2449"
 	},
 	"engines": {
 		"node": ">=20.10.0",

tools/gutenberg/build-gutenberg.js

@@ -148,7 +148,7 @@ async function main() {
 				? '--base-url="includes_url( \'build\' )"'
 				: "--base-url=includes_url( 'build' )";
 
-		await exec( 'npm', [ 'run', 'build', '--', baseUrlArg ], {
+		await exec( 'npm', [ 'run', 'build', '--', '--fast', baseUrlArg ], {
 			cwd: gutenbergDir,
 		} );