Add ability to use clang with GNU toolchain on Haiku

[am11]

With this and #126701, clang (with Haiku-specific GNU toolchain) passes runtime build.
i.e.

$ podman run --rm -v ${pwd}:/runtime -w /runtime -e ROOTFS_DIR=/crossrootfs/x64 \
    mcr.microsoft.com/dotnet-buildtools/prereqs:azurelinux-3.0-net11.0-cross-haiku-amd64 \
      src/coreclr/build-runtime.sh -cross -os haiku

...
Repo successfully built.
Product binaries are available at /runtime/artifacts/bin/coreclr/haiku.x64.Debug

[am11]

cc @trungnt2910

[am11]

eng/common changes upstreamed dotnet/arcade#16756

[am11]

Now src/coreclr/build-runtime.sh -cross -os haiku works with -gcc as well (that gcc binary is cross linux-x64 which comes from haiku's rootfs). @trungnt2910, just FYI, when we switch between gcc and clang, we must delete the previously built intermediate dir (rm -rf artifacts/obj/coreclr/haiku.x64.*) Incremental builds across compiler is not possible.

[am11]

@jkoritzinsky, thanks. Could you please merge upstream PR (dotnet/arcade#16756) as well to keep them in sync?