microbundle fails with '(terser plugin) Error: Call retries were exceeded'

`microbundle` launches, produces some warnings, and after 6 minutes fails with a terser error:

```
$ date; npm run build
Mon Oct 25 14:46:49 BST 2021

> @company/myapp-api-functions@2.0.2 build
> microbundle

Failed to resolve the module util imported by util?commonjs-external
Is the module installed? Note:
↳ to inline a module into your bundle, install it to "devDependencies".
↳ to depend on a module via import/require, install it to "dependencies".
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/json/builder.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/json/builder.js -> /home/mike/Code/company/myapp-api-functions/node_modules/aws-sdk/lib/util.js?commonjs-proxy -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/json/parser.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/protocol/helpers.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/protocol/helpers.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/json.js -> node_modules/aws-sdk/lib/protocol/helpers.js -> /home/mike/Code/company/myapp-api-functions/node_modules/aws-sdk/lib/core.js?commonjs-proxy -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/query.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/query.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/query.js -> node_modules/aws-sdk/lib/query/query_param_serializer.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/query.js -> node_modules/aws-sdk/lib/model/shape.js -> node_modules/aws-sdk/lib/model/collection.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/query.js -> node_modules/aws-sdk/lib/model/shape.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/rest.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/rest_json.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/rest_xml.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/protocol/rest_xml.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/xml/builder.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/model/api.js -> node_modules/aws-sdk/lib/model/operation.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/model/api.js -> node_modules/aws-sdk/lib/model/paginator.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/model/api.js -> node_modules/aws-sdk/lib/model/resource_waiter.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/model/api.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/sequential_executor.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/service.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/service.js -> node_modules/aws-sdk/lib/region_config.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/config.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/config.js -> node_modules/aws-sdk/lib/credentials.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/config.js -> node_modules/aws-sdk/lib/credentials/credential_provider_chain.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/http.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/event_listeners.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/event_listeners.js -> node_modules/aws-sdk/lib/discover_endpoint.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/util.js -> node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/event_listeners.js -> node_modules/aws-sdk/lib/discover_endpoint.js -> node_modules/aws-sdk/lib/util.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/request.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/response.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/resource_waiter.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/v2.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/v3.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/v3https.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/v4.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/v4.js -> node_modules/aws-sdk/lib/signers/v4_credentials.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/s3.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/signers/request_signer.js -> node_modules/aws-sdk/lib/signers/presign.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/core.js -> node_modules/aws-sdk/lib/param_validator.js -> node_modules/aws-sdk/lib/core.js
Circular dependency: node_modules/aws-sdk/lib/browser_loader.js -> node_modules/aws-sdk/lib/credentials/temporary_credentials.js -> node_modules/aws-sdk/clients/sts.js -> node_modules/aws-sdk/lib/browser_loader.js
Circular dependency: node_modules/aws-sdk/lib/browser_loader.js -> node_modules/aws-sdk/lib/credentials/temporary_credentials.js -> node_modules/aws-sdk/clients/sts.js -> /home/mike/Code/company/myapp-api-functions/node_modules/aws-sdk/lib/browser_loader.js?commonjs-proxy -> node_modules/aws-sdk/lib/browser_loader.js
Circular dependency: node_modules/aws-sdk/lib/browser_loader.js -> node_modules/aws-sdk/lib/credentials/cognito_identity_credentials.js -> node_modules/aws-sdk/clients/cognitoidentity.js -> node_modules/aws-sdk/lib/browser_loader.js

Call retries were exceeded

(terser plugin) Error: Call retries were exceeded
Error: Call retries were exceeded
at ChildProcessWorker.initialize (/home/mike/Code/company/myapp-api-functions/node_modules/rollup-plugin-terser/node_modules/jest-worker/build/workers/ChildProcessWorker.js:193:21)
at ChildProcessWorker._onExit (/home/mike/Code/company/myapp-api-functions/node_modules/rollup-plugin-terser/node_modules/jest-worker/build/workers/ChildProcessWorker.js:274:12)
at ChildProcess.emit (events.js:400:28)
at Process.ChildProcess._handle.onexit (internal/child_process.js:277:12)

```