Also set CT_DEBUGROOT_DIR for non sysroot-ed toolchains.

In the non-sysroot-ed case, the debuf-root directory would not be set;
debug tools would have been installed God-only-knows-where...

Spotted by Bart van der Meulen <bartvdrmeulen@gmail.com>.

 # x86 specific options

 config ARCH_x86

     select ARCH_USE_MMU

     select ARCH_SUPPORT_ARCH

     select ARCH_SUPPORT_CPU

     select ARCH_SUPPORT_TUNE

     help

       The x86 architecture, as defined by:

         http://www.intel.com/