Support for custom properties passed to the action

[cmboling]

Include a field to add custom properties to FOSSA analysis. Some users are dealing with custom builds which require custom properties to be passed to the invocation.

@NielsDoucet provided a use case where a custom gradle wrapper is used where custom system properties are passed (e.g. ./gradlew -Dany.system.prop=value)

jobs:
  fossa-scan:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: fossas/fossa-action@main # Use a specific version if locking is preferred
        with:
          api-key: ${{secrets.fossaApiKey}}
          - gradle:
            - system-properties:
              sys.prop1: value1
              sys.prop2: value2
            - properties:
              prop1: value1
              prop2: value2

[NielsDoucet]

For extra context: https://docs.gradle.org/current/userguide/build_environment.html#sec:gradle_system_properties
The relevant properties to define credentials to download a custom distribution are:

systemProp.gradle.wrapperUser=myuser
systemProp.gradle.wrapperPassword=mypassword

[NielsDoucet]

I did some further digging into the issue and I'm now convinced this can't be solved exclusively at the GitHub action level. This requires the fossa cli tool to adapt how it invokes gradle. This issue should probably be moved to the fossa-cli tool repository.

[cmboling]

@NielsDoucet Done.