Correctly handle V= only from command line, not from environment.

/trunk/ct-ng.in | 17 8 9 0 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

 # Compute x86_64-specific values

 CT_DoArchValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}"

 }