[Build System] moe-core does not always generate icugen *.spp files

[Berstanio]

I ran into the issue, when doing MOE ci builds, that sometimes doing "./gradlew build" does not always ensure, that the icu *.spp files get generated. Running "./gradlew build" again fixes this issue.
However, especially for ci, it would be good to have a reliable "build" task-