Mk/bsd.port.mk: Add EXTRACT_ENV

[des]

Summary

Add an EXTRACT_ENV variable which defaults to LC_ALL=C.UTF-8. We set
LC_ALL=C globally to ensure our scripts work the way we intend them to,
but this causes tar and unzip to fail to extract distfiles containing
names that cannot be expressed in ASCII. This was previously masked by
a bug in libarchive which caused tar and unzip to fail to notice that
these names were unconvertible and just pass them through unchanged.

MFH: 2026Q2

[arrowd]

Mk/bsd.port.mk

3214

Shouldn't this also have ${SETENV} before ${EXTRACT_ENV}. This is how all other *_ENV knobs are used.

[des]

Mk/bsd.port.mk

3214

I can add it for consistency's sake, but it isn't actually needed, and it adds a small amount of overhead.