When we create a PDB file using PDBFileBuilder, the information
in the superblock, such as the size of the resulting file, is not
available.
Previously, PDBFileBuilder::initialize took a superblock assuming
that all the members of the struct are correct. That is useful when
you want to restore the exact information from a YAML file, but
that's probably the only use case in which that is useful.
When we are creating a PDB file on the fly, we have to backfill the
members.
This patch redefines PDBFileBuilder::initialize to take only a
block size. Now all the other members are left as default values,
so that they'll be updated when commit() is called.
Is the only difference in the two check prefixes the number of blocks? If so I would just delete the value and leave one check statement (see the NumDirectoryBytes field, or the NumStreams field, for example.