Changes

testenv: run: add --autoreconf-in-src-copy arg

Add a new argument that avoids the problem that ./configure refuses to
run if it has already been executed in the source dir. (It aborts and
asks the user to run "make distclean" first, which is especially
annoying if it has to be done in multiple source dirs before being able
to build successfully.)

Put the new logic behind am "experimental argument" for now. I think it
improves usability greatly and plan to make it the default later when
it has been well tested.

I have also considered making the source dir read-only when mounted into
podman and this argument is set. This was the original goal of Lynxis'
related patch, on which idea this one is based. But osmo-dev still
needs to write into the source dir in case it clones a new repository,
so making the sources dir read-only with this trade-off should be a
separate flag and could be added in another patch later.

Related: osmo-ttcn3-hacks I0f1ac8852218f158ece14c176f05574f60d9d1f7
Depends: osmo-dev I18ac50e3441df81e1fe7d8d5321df7e80ab9c650
Change-Id: I5c38ce69dc39823d12be574c74a654d2fa6ed8fb