The name of the debug log written by the cc compiler wrapper was given
by Spec.short_spec, which includes the architecture. Somewhere along
the line Spec.format started adding spaces around the architecture
property so the filename started including spaces; the cc wrapper
script appears to ignore this, so files like spack-cc-bzip2-....in.log
(which record the wrapped compiler invocations) were not being
generated. This uses a different format string from the spec to
generate the wrapper log file names (which does not include spaces).
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