ci : Restore ROCm job for Ubuntu (#27399)

* Revert "ci : disable ubuntu-rocm (#26969)"

This reverts commit 9558fa44c92746a58dd07ad1bf0c889715b938a6.

* ci: set ccache compiler_check=content for ROCm build

The ROCm toolchain is pip-installed fresh on every run, so the clang binary's
mtime changes each time. With ccache's default compiler_check=mtime that
invalidates the whole cache and warm builds only reached ~70% hits. Hash the
compiler contents instead so the cache survives toolchain reinstalls.

* Update ccache size to 1GB

We're waivering with so many architectures built, we need a bigger
ccache limit.

* merge fix

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Co-authored-by: Jim Wu <ywu@xilinx.com>
Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@huggingface.co>