Loose mode autotools (just configure-ish thing)

[Artoria2e5]

The good old way of using a configure script to generate a Makefile may not necessarily involve GNU's autotools. However, as long as the arguments to the configure script are compatible, arguably using our current autotools parameter presets is better than writing a build.sh script. (Ease, consistency, etc.)

Therefore we should introduce a boolean parameter to specify a "just configure" loose mode which disables all other advanced features when turned on. The herementioned advanced features may include:

• autoreconf has to be disabled.
• Automatic target/host triplet tagging. We may also use a common parameter to make the script tolerate invalid args.
• Version & Bug URL, same as above.

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