scripts: use CT_CONFIG_SHELL instead of CT_SHELL

CT_SHELL is undefined.
Thus, the generated wrapper scripts are not executable by the kernel
because they do not contain a valid interpreter.
Use CT_CONFIG_SHELL instead.

Signed-off-by: "Titus von Boxberg" <titus@v9g.de>

 reporter_name="dsreed on freenode/#crosstool-ng"

 reporter_url=""

 reporter_comment="Enables experimental support for VFP/NEON hardware floating point."