scripts: fix double slash in paths

Computed paths may contain double slashes.
This is not an issue but it is just ugly to look at.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="Ioannis E. VENETIS"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00109.html"

 reporter_comment=""