improve error message during the build process

When we build using the unified build process and something bad happen when installing plugins the error is confusing and hard to debug.

We should consider the following:
1. Improve that message
2. Remove the retry.
3. Add more verbosity but less than DEBUG=1.

```
Successfully installed bundler-1.9.10
Invoking bundler install...
Error Bundler::InstallError, retrying 1/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 2/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 3/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 4/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 5/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 6/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 7/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 8/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 9/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Error Bundler::InstallError, retrying 10/10
An error occurred while installing logstash-core-event-java (5.0.0), and Bundler cannot continue.
Make sure that `gem install logstash-core-event-java -v '5.0.0'` succeeds before bundling.
WARNING: SSLSocket#session= is not supported
Too many retries, aborting, caused by Bundler::InstallError
rake aborted!
```

Start by locating the unified build process entry point that invokes Bundler to install plugins, then reproduce the shown Bundler::InstallError output. Done means the installation failure message is clearer, retries are removed, and additional non-DEBUG verbosity explains the failure without repeating the same output.

Written by the indexing model from the issue text.