zero output_channels to skip B2A CLUT

We check output_channels to know whether to skip B2A CLUTs:

    if (dstProfile->B2A.output_channels) {
        *ops++  = Op_clamp;
        *ops++  = Op_clut_B2A;
        *args++ = &dstProfile->B2A;
        ...

This fixes the added fuzz case, a B2A profile with no CLUT.

The new profile doesn't quite dump the same when using MSVC's C stdlib,
so I've disabled it when defined(_MSC_VER).  Will follow up.

Bug: oss-fuzz:33396
Change-Id: I0c7e73ab5dfde652fd5f72e3f31429b2c249f7d9
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/399042
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed