After JDK-8360707 builds which omit C1 or C2 can generate an exploded jdk which fails on startup with an assert:

    assert(idx2 >= 0 && idx2 >= idx1) failed: bad blob ids first -1 and second -1

The problem is that the blob and stub id verification expects the blob, stub and entry ranges in the C1 and C2 stub groups to be positive. However, when C1 or C2 is omitted the associated range starts and ends are NO_BLOBID, NO_STUBID and NO_ENTRYID (all -1) and this breaks some of the internal consistency checks that test the span of blob, stub and entry ranges.