Point bdwgc submodule to commit that includes prefetch on MSVC

[sschoener]

• Should this pull request have release notes?
  • Yes
  • No
• Do these changes need to be back ported?
  • Yes
  • No
• Do these changes need to be upstreamed to mono/mono or dotnet/runtime repositories?
  • Yes
  • No

Reviewers: please consider these questions as well! ❤️

[richardkettlewell]

i think you arent handling NO_PREFETCH properly anymore.

[sschoener]

@richardkettlewell Thanks! Grepping for this also revealed that gc_inline.h is also defining the prefetch macros separately, so this probably needs to be fixed up as well.

[joncham]

Thanks for this work @sschoener ! I added a comment to the bdwgc change; my only worry is that this may clash with recent @jem-patel ARM64 work. I would suggest rebasing this PR on top of unity-main to ensure the Win ARM64 target continues to build.

Additionally, this change will eventually impact IL2CPP once we bump the submodule there. I will kick off a test run with these change in IL2CPP as well. cc @joshpeterson

[joncham]

cc @TautvydasZilys as well

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