config: checkout hipparchus to certain SHA to make build stable
config: checkout hipparchus to certain SHA to make build stable

rnveach/checkstyle,checkstyle/checkstyle,romani/checkstyle,romani/checkstyle,romani/checkstyle,checkstyle/checkstyle,rnveach/checkstyle,rnveach/checkstyle,rnveach/checkstyle,romani/checkstyle,rnveach/checkstyle,romani/checkstyle,rnveach/checkstyle,checkstyle/checkstyle,checkstyle/checkstyle,checkstyle/checkstyle,checkstyle/checkstyle,romani/checkstyle