bake: correctly match error when parsing definition

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

src/buildx/bake.ts

@@ -77,7 +77,7 @@ export class Bake {
       silent: true
     }).then(res => {
       if (res.stderr.length > 0 && res.exitCode != 0) {
-        throw new Error(res.stderr);
+        throw new Error(`cannot parse bake definitions: ${res.stderr.match(/(.*)\s*$/)?.[0]?.trim() ?? 'unknown error'}`);
       }
       return <BakeDefinition>JSON.parse(res.stdout.trim());
     });