Build extensions not found

[ttuegel]

mvn2nix does not consider build extensions such as found in kframework/k. As a result, attempting to build with buildMaven fails:

  [ERROR]   The project com.runtimeverification.k:parent:1.0-SNAPSHOT (/build/k/pom.xml) has 1 error
  [ERROR]     Unresolveable build extension: Plugin org.springframework.build:aws-maven:5.0.0.RELEASE or one of its dependencies could not be resolved: Cannot access central (https://repo.maven.apache.org/maven2) in offline mode and the artifact org.springframework.build:aws-maven:jar:5.0.0.RELEASE has not been downloaded from it before. -> [Help 2]
  [ERROR] 
  [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
  [ERROR] Re-run Maven using the -X switch to enable full debug logging.
  [ERROR] 
  [ERROR] For more information about the errors and possible solutions, please read the following articles:
  [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/ProjectBuildingException
  [ERROR] [Help 2] http://cwiki.apache.org/confluence/display/MAVEN/PluginManagerException

I believe build extensions could be handled by extending the code that finds plugins, but my Java is weak.

[cartazio]

yeah, @shlevy et al, any legs on this?