scripts: fix broken variable name

This patch fixes a config variable name missing its 'CT_' prefix.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

 reporter_name="Yann E. MORIN"

 reporter_url="http://ymorin.is-a-geek.org/projects/crosstool"

 reporter_comment="EXPERIMENTAL MIPS-64 n64 toolchain."