[ANY] Maven build fails for client generation and no jar file is created.

Description

I'm following the Readme file (Getting Started) to generate a PHP client. The following error happens after running mvn clean package

[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] swagger-codegen-project 3.0.3 ...................... SUCCESS [  9.209 s]
[INFO] swagger-codegen (core library) ..................... FAILURE [01:08 min]
[INFO] swagger-codegen (executable) ....................... SKIPPED
[INFO] swagger-codegen (maven-plugin) ..................... SKIPPED
[INFO] swagger-generator 3.0.3 ............................ SKIPPED
,
       "summary": "Finds Pets by tags",
       "description": "Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.",
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------

The swagger-codegen-cli.jar file does not get generated, so running the next command:

java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar generate \
  -i http://petstore.swagger.io/v2/swagger.json \
  -l php \
  -o /var/tmp/php_api_client

produces

Error: Unable to access jarfile modules/swagger-codegen-cli/target/swagger-codegen-cli.jar

Swagger-codegen version

ANY

Swagger declaration file content or url

ANY

Command line used for generation

git clone https://github.com/swagger-api/swagger-codegen
cd swagger-codegen
mvn clean package
java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar generate \
   -i http://petstore.swagger.io/v2/swagger.json \
   -l php \
   -o /var/tmp/php_api_client 

Related issues/PRs

https://github.com/swagger-api/swagger-codegen/issues/8734

Reproduce the README Getting Started commands with mvn clean package from the cloned repository. Start with the full failure in the swagger-codegen (core library) module, then compare the report with related issue 8734. Done means the build completes, modules/swagger-codegen-cli/target/swagger-codegen-cli.jar exists, and the documented PHP generation command can run.