scripts: Use ${CT_TARGET}-strip to strip gdbserver

Signed-off-by: Zhenqiang Chen <zhenqiang.chen@linaro.org>
[yann.morin.1998@free.fr: quote variables]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <CACgzC7BU9CPZ2cE+EYqnMe2WNz-wYby6f4tsmjJi715WmPmbWw@mail.gmail.com>
PatchWork-Id: 185303

 # m68k specific configuration file

 ## depends on EXPERIMENTAL

 ##

 ## select ARCH_SUPPORTS_32

 ## select ARCH_DEFAULT_32

 ## select ARCH_DEFAULT_BE

 ## select ARCH_SUPPORTS_WITH_CPU

 ##

 ## help The m68k architecture