BaseTools/GenFw: disregard payload in PE debug directory entry size

BaseTools/GenFw: disregard payload in PE debug directory entry size

Currently, the PE/COFF conversion routines in GenFw add a so-called
NB10 CodeView debug record to the image, and update the associated
directory entry in the PE/COFF optional header to contain its relative
virtual address (RVA) and size.

However, there are two levels of indirection at work here: the actual
NB10 CodeView record (which is simply a magic number and some unused
data fields followed by the NUL terminated filename) is emitted
separately, and a separate descriptor is emitted that identifies the
NB10 CodeView record as type EFI_IMAGE_DEBUG_TYPE_CODEVIEW, and records
its size. The directory entry in the PE/COFF optional header should
refer to this intermediate descriptor's address and size only, but
the WriteDebug## () routines in GenFw erroneously record the size of
both the descriptor and the NB10 CodeView record.

This problem was exposed by commit e4129b0e5897 ("BaseTools: Update
GenFw to clear unused debug entry generated by VS tool chain",
2017-06-19), and GenFw now crashes when it attempts to iterate over
what it thinks are multiple intermediate descriptors for different
kinds of debug data embedded in the image.

The error is understandable, given that both are carved out of the
same file space allocation, but this is really an implementation detail
of GenFw, and is not required. (Note that the intermediate descriptor
does not require a RVA and so it does not even need to be inside a
section)

So omit the size of the NB10 CodeView record from the size recorded
in the optional header.

Link: https://lists.01.org/pipermail/edk2-devel/2017-July/012162.html
Link: https://lists.01.org/pipermail/edk2-devel/2017-July/012181.html
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Co-debugged-or-whatever-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>