Build error: Could not resolve entry packages/true/index.js

[d9k]

> rm -r node_modules
> node --version
v14.17.0
> yarn --version
1.22.11
> yarn
. . . . .
Done in 14.26s.
> yarn build
(!) You have passed an unrecognized option
Unknown output options: sourceMap. Allowed options: amd, assetFileNames, banner, chunkFileNames, compact, dir, dynamicImportFunction, entryFileNames, esModule, exports, extend, externalLiveBindings, file, footer, format, freeze, globals, hoistTransitiveImports, indent, inlineDynamicImports, interop, intro, manualChunks, minifyInternalExports, name, namespaceToStringTag, noConflict, outro, paths, plugins, preferConst, preserveModules, preserveModulesRoot, sourcemap, sourcemapExcludeSources, sourcemapFile, sourcemapPathTransform,
strict, systemNullSetters

packages/true/index.js → packages/true/build...
no items to copy
[!] Error: Could not resolve entry module (packages/true/index.js).
Error: Could not resolve entry module (packages/true/index.js).
    at error (/home/d9k/repos/nib/node_modules/rollup/dist/shared/rollup.js:5253:30)
    at ModuleLoader.loadEntryModule (/home/d9k/repos/nib/node_modules/rollup/dist/shared/rollup.js:18424:20)
    at async Promise.all (index 0)

error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.