Description of problem:
dotnet6.0 bootstrap builds hang when using components built with clang/llvm > 12.0.1

Version-Release number of selected component (if applicable):
clang-13.0.0~rc1-1.fc35.x86_64 & llvm-13.0.0~rc1-1.fc35.x86_64
clang-13.0.0-3.fc35.x86_64 & llvm-13.0.0-4.fc35.x86_64

How reproducible:
Always.

Steps to Reproduce:
(from https://github.com/dotnet/runtime/issues/61671)

    git clone https://pagure.io/dotnet-sig/dotnet6.0.git
    cd dotnet6.0
    git checkout abafa176a7ac41bc6b2ebf84040bd39bca21c15a
    sudo dnf build-dep dotnet5.0 -y
    ./build-dotnet-tarball --bootstrap 9e8b04bbff820c93c142f99a507a46b976f5c14c
    # Wait
    fedpkg --release f35 local
    # After an hour or so, build hangs

Actual results:
crossgen2 hangs, causing bootstrap to stall

Expected results:
dotnet6.0 bootstraps successfully

Additional info:
As described in https://pagure.io/dotnet-sig/dotnet6.0/issue/1#comment-762682, otherwise-identical builds using clang-12.0.1/llvm12-libs-12.0.1-2 do not exhibit the issue.