Ignore _merged_spec.yaml when computing build cache key

[jprinet]

Issue

The build has some cache misses when run twice without any change (on a fresh clone). The cost here is 10s of wall clock time:

The problem is that the file modules/openapi-generator-maven-plugin/src/test/resources/default/_merged_spec.yaml generated by the maven-plugin module tests is located in the src/test/resources folder which is used as goal input by compiler:testCompile and surefire:test from the maven-plugin module.

This means that the cache key is different, therefore the cache misses.

Steps to reproduce

Clone the project in a new location

git clone [email protected]:OpenAPITools/openapi-generator.git /tmp/openapi-generator
cd /tmp/openapi-generator
./mvnw clean package
./mvnw clean package

Fix

The best solution would be to generate the _merged_spec.yaml in the target directory, however I couldn't find a way to configure this.
The approach taken is to ignore the file while computing the cache key with help of RuntimeNormalization.

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  ./mvnw clean package 
  ./bin/generate-samples.sh ./bin/configs/*.yaml
  ./bin/utils/export_docs_generators.sh
  

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