Someof the mingw32 source tarballs have an appended '-src' after the
version.
Since changeset #6e1412ba8da9 (scripts/functions: force extract folder
to archive basename), it means mingw tarballs get extracted in a directory
ending with '-src'.
Fix that.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>