In compiler bootstrapping pipelines, we add an artificial dependency
between jobs for packages to be built with a bootstrapped compiler
and the job building the compiler. To find the right bootstrapped
compiler for each spec, we compared not only the compiler spec to
that required by the package spec, but also the architectures of
the compiler and package spec.
But this prevented us from finding the bootstrapped compiler for a
spec in cases where the architecture of the compiler wasn't exactly
the same as the spec. For example, a gcc@4.8.5 might have
bootstrapped a compiler with haswell as the architecture, while the
spec had broadwell. By comparing the families instead of the architecture
itself, we know that we can build the zlib for broadwell with the gcc for
haswell.
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