scripts/functions: fix debug-shell

Properly catch resuming the build when continuing past the
failed command.

The 'case ;;&' construct is a bash4ism. Get rid of it.

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

 # windows config options

 ## depends on EXPERIMENTAL && ARCH_x86

 ##

 ## select WINDOWS

 ##

 ## help Build a toolchain targeting systems running Windows as host