[3.0] configure.ac: Allow passing VLC_COMPILE_BY and VLC_COMPILE_HOST.

This allows passing a specific value instead of inheriting these values from the build environment.

Fixes #26035 (closed)

(cherry picked from commit 9e7ed024) (edited)

edited:

• the 3.0 branch doesn't have [] around the variable names

Signed-off-by: Steve Lhomme robux4@ycbcr.xyz