[issue38443] unavailable --with-universal-archs= macOS confgure options fail cryptically

[Ned Deily]

New submission from Ned Deily <nad at python.org>:

./configure's --with-universal-archs= supports a number of different CPU architecture combinations.  However most of them are no longer supported on current macOS systems.  If you choose an option with archs not available in the build tool chain in use, the configure script fails in various cryptic ways, usually with multiple configure test failures like:

checking dlfcn.h presence... yes
configure: WARNING: dlfcn.h: present but cannot be compiled
configure: WARNING: dlfcn.h:     check for missing prerequisite headers?
configure: WARNING: dlfcn.h: see the Autoconf documentation
configure: WARNING: dlfcn.h:     section "Present But Cannot Be Compiled"
configure: WARNING: dlfcn.h: proceeding with the compiler's result
configure: WARNING:     ## --------------------------------------- ##
configure: WARNING:     ## Report this to https://bugs.python.org/ ##
configure: WARNING:     ## --------------------------------------- ##

./configure should be more user-friendly here.  At a minimum, it should report near the beginning exactly which archs are going to be tested; it already reports the --with-universal-archs value.  Even better it should explicitly test for support of each arch in the build tool chain in use and stop if any of the requested archs are not available.

----------
components: Build, macOS
messages: 354429
nosy: ned.deily, ronaldoussoren
priority: normal
severity: normal
stage: needs patch
status: open
title: unavailable --with-universal-archs= macOS confgure options fail cryptically
versions: Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue38443>
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