Cannot use LESS mixins in Live Data vue templates

[INFO] --- frontend-maven-plugin:1.11.0:npm (npm-run-build) @ xwiki-platform-livedata-webjar ---
[INFO] Running 'npm run build' in /home/marius/work/git/xwiki/xwiki-platform/xwiki-platform-core/xwiki-platform-livedata/xwiki-platform-livedata-webjar/target/vue
[INFO] 
[INFO] > xwiki-livedata-vue@1.0.0 build /home/marius/work/git/xwiki/xwiki-platform/xwiki-platform-core/xwiki-platform-livedata/xwiki-platform-livedata-webjar/target/vue
[INFO] > vue-cli-service build --target lib --formats umd-min XWikiLivedata.vue
[INFO] 
[INFO] 
[INFO] -  Building for production as library (umd-min)...
[INFO]  ERROR  Failed to compile with 2 errors11:37:40 AM
[INFO] 
[INFO]  error  in ./LivedataPagination.vue?vue&type=style&index=0&lang=css&
[INFO] 
[INFO] SyntaxError
[INFO] 
[INFO] (279:3) Unknown word
[INFO] 
[INFO]   277 | 
[INFO]   278 | .livedata-pagination {
[INFO] > 279 |   .text-muted-smaller;
[INFO]       |   ^
[INFO]   280 |   margin-left: 1rem;
[INFO]   281 | }
[INFO] 
[INFO] 
[INFO]  ERROR  Build failed with errors.
[INFO]  @ ./LivedataPagination.vue?vue&type=style&index=0&lang=css& 1:0-430 1:0-430
[INFO]  @ ./LivedataPagination.vue
[INFO]  @ ./node_modules/cache-loader/dist/cjs.js??ref--12-0!./node_modules/thread-loader/dist/cjs.js!./node_modules/babel-loader/lib!./node_modules/cache-loader/dist/cjs.js??ref--0-0!./node_modules/vue-loader/lib??vue-loader-options!./layouts/table/LayoutTable.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/table/LayoutTable.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/table/LayoutTable.vue
[INFO]  @ ./layouts lazy ^\.\/.*\.vue$ namespace object
[INFO]  @ ./node_modules/cache-loader/dist/cjs.js??ref--12-0!./node_modules/thread-loader/dist/cjs.js!./node_modules/babel-loader/lib!./node_modules/cache-loader/dist/cjs.js??ref--0-0!./node_modules/vue-loader/lib??vue-loader-options!./layouts/LivedataLayout.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/LivedataLayout.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/LivedataLayout.vue
[INFO]  @ ./node_modules/cache-loader/dist/cjs.js??ref--12-0!./node_modules/thread-loader/dist/cjs.js!./node_modules/babel-loader/lib!./node_modules/cache-loader/dist/cjs.js??ref--0-0!./node_modules/vue-loader/lib??vue-loader-options!./XWikiLivedata.vue?vue&type=script&lang=js&
[INFO]  @ ./XWikiLivedata.vue?vue&type=script&lang=js&
[INFO]  @ ./XWikiLivedata.vue
[INFO]  @ ./node_modules/@vue/cli-service/lib/commands/build/entry-lib.js
[INFO] 
[INFO]  error  in ./LivedataTopbar.vue?vue&type=style&index=0&lang=less&
[INFO] 
[INFO] SyntaxError
[INFO] 
[INFO] (73:3) Unknown word
[INFO] 
[INFO]   71 |   }
[INFO]   72 | 
[INFO] > 73 |   .flat-buttons();
[INFO]      |   ^
[INFO]   74 | }
[INFO]   75 | 
[INFO] 
[INFO] 
[INFO]  @ ./LivedataTopbar.vue?vue&type=style&index=0&lang=less& 1:0-430 1:0-430
[INFO]  @ ./LivedataTopbar.vue
[INFO]  @ ./node_modules/cache-loader/dist/cjs.js??ref--12-0!./node_modules/thread-loader/dist/cjs.js!./node_modules/babel-loader/lib!./node_modules/cache-loader/dist/cjs.js??ref--0-0!./node_modules/vue-loader/lib??vue-loader-options!./layouts/table/LayoutTable.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/table/LayoutTable.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/table/LayoutTable.vue
[INFO]  @ ./layouts lazy ^\.\/.*\.vue$ namespace object
[INFO]  @ ./node_modules/cache-loader/dist/cjs.js??ref--12-0!./node_modules/thread-loader/dist/cjs.js!./node_modules/babel-loader/lib!./node_modules/cache-loader/dist/cjs.js??ref--0-0!./node_modules/vue-loader/lib??vue-loader-options!./layouts/LivedataLayout.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/LivedataLayout.vue?vue&type=script&lang=js&
[INFO]  @ ./layouts/LivedataLayout.vue
[INFO]  @ ./node_modules/cache-loader/dist/cjs.js??ref--12-0!./node_modules/thread-loader/dist/cjs.js!./node_modules/babel-loader/lib!./node_modules/cache-loader/dist/cjs.js??ref--0-0!./node_modules/vue-loader/lib??vue-loader-options!./XWikiLivedata.vue?vue&type=script&lang=js&
[INFO]  @ ./XWikiLivedata.vue?vue&type=script&lang=js&
[INFO]  @ ./XWikiLivedata.vue
[INFO]  @ ./node_modules/@vue/cli-service/lib/commands/build/entry-lib.js
[INFO] 
[INFO] npm ERR! code ELIFECYCLE
[INFO] npm ERR! errno 1
[INFO] npm ERR! xwiki-livedata-vue@1.0.0 build: `vue-cli-service build --target lib --formats umd-min XWikiLivedata.vue`
[INFO] npm ERR! Exit status 1
[INFO] npm ERR! 
[INFO] npm ERR! Failed at the xwiki-livedata-vue@1.0.0 build script.
[INFO] npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
[INFO] 
[INFO] npm ERR! A complete log of this run can be found in:
[INFO] npm ERR!     /home/marius/.npm/_logs/2021-04-19T08_37_40_767Z-debug.log