implicitly download and add the haxe std-java.jar dependency to build.hxml

[ScrambledRK]

when generating the build.hxml to convert haxe to java - it is necessary to exclude the haxe standard library but at the same time reference it. it is possible to generate a single jar for the standard library. this library is a normal maven dependency and must be resolved as such. (downloaded from a maven repository). the hxml requires the -java-lib path parameter to be set to this artifact.