configure: fix version string breakage

As we use the directory names as Makefile targets, they can not contain any
column ':', or else make will complain about 'multiple target patterns'.

Replace the offending ':' with a dash '-', as Titus suggested.

Reported-by: Erdem Budak <erdembudak@hotmail.com>
Reported-by: Titus von Boxberg <titus@v9g.de>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Alpha specific configuration file

## select ARCH_SUPPORTS_32

## select ARCH_DEFAULT_32

## select ARCH_USE_MMU

## select ARCH_SUPPORT_CPU

## select ARCH_SUPPORT_TUNE

##

## help The Alpha architecture.